Screw n.
 1. A cylinder, or a cylindrical perforation, having a continuous rib, called the thread, winding round it spirally at a constant inclination, so as to leave a continuous spiral groove between one turn and the next, -- used chiefly for producing, when revolved, motion or pressure in the direction of its axis, by the sliding of the threads of the cylinder in the grooves between the threads of the perforation adapted to it, the former being distinguished as the external, or male screw, or, more usually the screw; the latter as the internal, or female screw, or, more usually, the nut.
 Note: ☞ The screw, as a mechanical power, is a modification of the inclined plane, and may be regarded as a right-angled triangle wrapped round a cylinder, the hypotenuse of the marking the spiral thread of the screw, its base equaling the circumference of the cylinder, and its height the pitch of the thread.
 2. Specifically, a kind of nail with a spiral thread and a head with a nick to receive the end of the screw-driver. Screws are much used to hold together pieces of wood or to fasten something; -- called also wood screws, and screw nails. See also Screw bolt, below.
 3. Anything shaped or acting like a screw; esp., a form of wheel for propelling steam vessels. It is placed at the stern, and furnished with blades having helicoidal surfaces to act against the water in the manner of a screw. See Screw propeller, below.
 4. A steam vesel propelled by a screw instead of wheels; a screw steamer; a propeller.
 5. An extortioner; a sharp bargainer; a skinflint; a niggard.
 6. An instructor who examines with great or unnecessary severity; also, a searching or strict examination of a student by an instructor. [Cant, American Colleges]
 7. A small packet of tobacco. [Slang]
 8. An unsound or worn-out horse, useful as a hack, and commonly of good appearance.
 9. Math. A straight line in space with which a definite linear magnitude termed the pitch is associated (cf. 5th Pitch, 10 (b)). It is used to express the displacement of a rigid body, which may always be made to consist of a rotation about an axis combined with a translation parallel to that axis.
 10. Zool. An amphipod crustacean; as, the skeleton screw (Caprella). See Sand screw, under Sand.
 Archimedes screw, Compound screw, Foot screw, etc. See under Archimedes, Compound, Foot, etc.
 A screw loose, something out of order, so that work is not done smoothly; as, there is a screw loose somewhere. --H. Martineau.
 Endless screw, or perpetual screw, a screw used to give motion to a toothed wheel by the action of its threads between the teeth of the wheel; -- called also a worm.
 Lag screw. See under Lag.
 Micrometer screw, a screw with fine threads, used for the measurement of very small spaces.
 Right and left screw, a screw having threads upon the opposite ends which wind in opposite directions.
 Screw alley. See Shaft alley, under Shaft.
 Screw bean. Bot. (a) The curious spirally coiled pod of a leguminous tree (Prosopis pubescens) growing from Texas to California. It is used for fodder, and ground into meal by the Indians. (b) The tree itself. Its heavy hard wood is used for fuel, for fencing, and for railroad ties.
 Screw bolt, a bolt having a screw thread on its shank, in distinction from a key bolt. See 1st Bolt, 3.
 Screw box, a device, resembling a die, for cutting the thread on a wooden screw.
 Screw dock. See under Dock.
 Screw engine, a marine engine for driving a screw propeller.
 Screw gear. See Spiral gear, under Spiral.
 Screw jack. Same as Jackscrew.
 Screw key, a wrench for turning a screw or nut; a spanner wrench.
 Screw machine. (a) One of a series of machines employed in the manufacture of wood screws. (b) A machine tool resembling a lathe, having a number of cutting tools that can be caused to act on the work successively, for making screws and other turned pieces from metal rods.
 Screw pine Bot., any plant of the endogenous genus Pandanus, of which there are about fifty species, natives of tropical lands from Africa to Polynesia; -- named from the spiral arrangement of the pineapple-like leaves.
 Screw plate, a device for cutting threads on small screws, consisting of a thin steel plate having a series of perforations with internal screws forming dies.
 Screw press, a press in which pressure is exerted by means of a screw.
 Screw propeller, a screw or spiral bladed wheel, used in the propulsion of steam vessels; also, a steam vessel propelled by a screw.
 Screw shell Zool., a long, slender, spiral gastropod shell, especially of the genus Turritella and allied genera. See Turritella.
 Screw steamer, a steamship propelled by a screw.
 Screw thread, the spiral rib which forms a screw.
 Screw stone Paleon., the fossil stem of an encrinite.
 Screw tree Bot., any plant of the genus Helicteres, consisting of about thirty species of tropical shrubs, with simple leaves and spirally twisted, five-celled capsules; -- also called twisted-horn, and twisty.
 Screw valve, a stop valve which is opened or closed by a screw.
 Screw worm Zool., the larva of an American fly (Compsomyia macellaria), allied to the blowflies, which sometimes deposits its eggs in the nostrils, or about wounds, in man and other animals, with fatal results.
 Screw wrench. (a) A wrench for turning a screw. (b) A wrench with an adjustable jaw that is moved by a screw.
 To put the screws on or To put the screw on, to use pressure upon, as for the purpose of extortion; to coerce.
 To put under the screw or To put under the screws, to subject to pressure; to force.
 Wood screw, a metal screw with a sharp thread of coarse pitch, adapted to holding fast in wood. See Illust. of Wood screw, under Wood.
 Wood, n.
 1. A large and thick collection of trees; a forest or grove; -- frequently used in the plural.
 Light thickens, and the crow
 Makes wing to the rooky wood.   --Shak.
 2. The substance of trees and the like; the hard fibrous substance which composes the body of a tree and its branches, and which is covered by the bark; timber.  “To worship their own work in wood and stone for gods.”
 3. Bot. The fibrous material which makes up the greater part of the stems and branches of trees and shrubby plants, and is found to a less extent in herbaceous stems. It consists of elongated tubular or needle-shaped cells of various kinds, usually interwoven with the shinning bands called silver grain.
 Note: ☞ Wood consists chiefly of the carbohydrates cellulose and lignin, which are isomeric with starch.
 4. Trees cut or sawed for the fire or other uses.
 Wood acid, Wood vinegar Chem., a complex acid liquid obtained in the dry distillation of wood, and containing large quantities of acetic acid; hence, specifically, acetic acid. Formerly called pyroligneous acid.
 Wood anemone Bot., a delicate flower (Anemone nemorosa) of early spring; -- also called windflower.  See Illust. of Anemone.
 Wood ant Zool., a large ant (Formica rufa) which lives in woods and forests, and constructs large nests.
 Wood apple Bot.. See Elephant apple, under Elephant.
 Wood baboon Zool., the drill.
 Wood betony. Bot. (a) Same as Betony. (b) The common American lousewort (Pedicularis Canadensis), a low perennial herb with yellowish or purplish flowers.
 Wood borer. Zool. (a) The larva of any one of numerous species of boring beetles, esp. elaters, longicorn beetles, buprestidans, and certain weevils.  See Apple borer, under Apple, and Pine weevil, under Pine. (b) The larva of any one of various species of lepidopterous insects, especially of the clearwing moths, as the peach-tree borer (see under Peach), and of the goat moths. (c) The larva of various species of hymenopterous of the tribe Urocerata.  See Tremex. (d) Any one of several bivalve shells which bore in wood, as the teredos, and species of Xylophaga. (e) Any one of several species of small Crustacea, as the Limnoria, and the boring amphipod (Chelura terebrans).
 Wood carpet, a kind of floor covering made of thin pieces of wood secured to a flexible backing, as of cloth. --Knight.
 Wood cell Bot., a slender cylindrical or prismatic cell usually tapering to a point at both ends. It is the principal constituent of woody fiber.
 Wood choir, the choir, or chorus, of birds in the woods. [Poetic] --Coleridge.
 Wood coal, charcoal; also, lignite, or brown coal.
 Wood cricket Zool., a small European cricket (Nemobius sylvestris).
 Wood culver Zool., the wood pigeon.
 Wood cut, an engraving on wood; also, a print from such an engraving.
 Wood dove Zool., the stockdove.
 Wood drink, a decoction or infusion of medicinal woods.
 Wood duck Zool. (a) A very beautiful American duck (Aix sponsa). The male has a large crest, and its plumage is varied with green, purple, black, white, and red. It builds its nest in trees, whence the name.  Called also bridal duck, summer duck, and wood widgeon. (b) The hooded merganser. (c) The Australian maned goose (Chlamydochen jubata).
 Wood echo, an echo from the wood.
 Wood engraver. (a) An engraver on wood. (b) Zool. Any of several species of small beetles whose larvae bore beneath the bark of trees, and excavate furrows in the wood often more or less resembling coarse engravings; especially, Xyleborus xylographus.
 Wood engraving. (a) The act or art engraving on wood; xylography. (b) An engraving on wood; a wood cut; also, a print from such an engraving.
 Wood fern. Bot. See Shield fern, under Shield.
 Wood fiber. (a) Bot. Fibrovascular tissue. (b) Wood comminuted, and reduced to a powdery or dusty mass.
 Wood fretter Zool., any one of numerous species of beetles whose larvae bore in the wood, or beneath the bark, of trees.
 Wood frog Zool., a common North American frog (Rana sylvatica) which lives chiefly in the woods, except during the breeding season. It is drab or yellowish brown, with a black stripe on each side of the head.
 Wood germander. Bot. See under Germander.
 Wood god, a fabled sylvan deity.
 Wood grass. Bot. See under Grass.
 Wood grouse. Zool. (a) The capercailzie. (b) The spruce partridge.  See under Spruce.
 Wood guest Zool., the ringdove. [Prov. Eng.]
 Wood hen. Zool. (a) Any one of several species of Old World short-winged rails of the genus Ocydromus, including the weka and allied species. (b) The American woodcock.
 Wood hoopoe Zool., any one of several species of Old World arboreal birds belonging to Irrisor and allied genera. They are closely allied to the common hoopoe, but have a curved beak, and a longer tail.
 Wood ibis Zool., any one of several species of large, long-legged, wading birds belonging to the genus Tantalus. The head and neck are naked or scantily covered with feathers. The American wood ibis (Tantalus loculator) is common in Florida.
 Wood lark Zool., a small European lark (Alauda arborea), which, like, the skylark, utters its notes while on the wing. So called from its habit of perching on trees.
 Wood laurel Bot., a European evergreen shrub (Daphne Laureola).
 Wood leopard Zool., a European spotted moth (Zeuzera aesculi) allied to the goat moth. Its large fleshy larva bores in the wood of the apple, pear, and other fruit trees.
 Wood lily Bot., the lily of the valley.
 Wood lock Naut., a piece of wood close fitted and sheathed with copper, in the throating or score of the pintle, to keep the rudder from rising.
 Wood louse Zool. (a) Any one of numerous species of terrestrial isopod Crustacea belonging to Oniscus, Armadillo, and related genera.  See Sow bug, under Sow, and Pill bug, under Pill. (b) Any one of several species of small, wingless, pseudoneuropterous insects of the family Psocidae, which live in the crevices of walls and among old books and papers.  Some of the species are called also book lice, and deathticks, or deathwatches.
 Wood mite Zool., any one of numerous small mites of the family Oribatidae. They are found chiefly in woods, on tree trunks and stones.
 Wood mote. Eng. Law (a) Formerly, the forest court. (b) The court of attachment.
 Wood nettle. Bot. See under Nettle.
 Wood nightshade Bot., woody nightshade.
 Wood nut Bot., the filbert.
 Wood nymph. a A nymph inhabiting the woods; a fabled goddess of the woods; a dryad.  “The wood nymphs, decked with daisies trim.” --Milton. (b) Zool. Any one of several species of handsomely colored moths belonging to the genus Eudryas. The larvae are bright-colored, and some of the species, as Eudryas grata, and Eudryas unio, feed on the leaves of the grapevine. (c) Zool. Any one of several species of handsomely colored South American humming birds belonging to the genus Thalurania. The males are bright blue, or green and blue.
 Wood offering, wood burnt on the altar.
    We cast the lots . . . for the wood offering.   --Neh. x. 34.
 -- Wood oil Bot., a resinous oil obtained from several East Indian trees of the genus Dipterocarpus, having properties similar to those of copaiba, and sometimes substituted for it. It is also used for mixing paint.  See Gurjun.
 Wood opal Min., a striped variety of coarse opal, having some resemblance to wood.
 Wood paper, paper made of wood pulp.  See Wood pulp, below.
 Wood pewee Zool., a North American tyrant flycatcher (Contopus virens). It closely resembles the pewee, but is smaller.
 Wood pie Zool., any black and white woodpecker, especially the European great spotted woodpecker.
 Wood pigeon. Zool. (a) Any one of numerous species of Old World pigeons belonging to Palumbus and allied genera of the family Columbidae. (b) The ringdove.
 Wood puceron Zool., a plant louse.
 Wood pulp Technol., vegetable fiber obtained from the poplar and other white woods, and so softened by digestion with a hot solution of alkali that it can be formed into sheet paper, etc. It is now produced on an immense scale.
 Wood quail Zool., any one of several species of East Indian crested quails belonging to Rollulus and allied genera, as the red-crested wood quail (Rollulus roulroul), the male of which is bright green, with a long crest of red hairlike feathers.
 Wood rabbit Zool., the cottontail.
 Wood rat Zool., any one of several species of American wild rats of the genus Neotoma found in the Southern United States; -- called also bush rat. The Florida wood rat (Neotoma Floridana) is the best-known species.
 Wood reed grass Bot., a tall grass (Cinna arundinacea) growing in moist woods.
 Wood reeve, the steward or overseer of a wood. [Eng.]
 Wood rush Bot., any plant of the genus Luzula, differing from the true rushes of the genus Juncus chiefly in having very few seeds in each capsule.
 Wood sage Bot., a name given to several labiate plants of the genus Teucrium.  See Germander.
 Wood screw, a metal screw formed with a sharp thread, and usually with a slotted head, for insertion in wood.
 Wood sheldrake Zool., the hooded merganser.
 Wood shock Zool., the fisher.  See Fisher, 2.
 Wood shrike Zool., any one of numerous species of Old World singing birds belonging to Grallina, Collyricincla, Prionops, and allied genera, common in India and Australia. They are allied to the true shrikes, but feed upon both insects and berries.
 Wood snipe. Zool. (a) The American woodcock. (b) An Asiatic snipe (Gallinago nemoricola).
 Wood soot, soot from burnt wood.
 Wood sore. Zool. See Cuckoo spit, under Cuckoo.
 Wood sorrel Bot., a plant of the genus Oxalis (Oxalis Acetosella), having an acid taste.  See Illust. (a) of Shamrock.
 Wood spirit. Chem. See Methyl alcohol, under Methyl.
 Wood stamp, a carved or engraved block or stamp of wood, for impressing figures or colors on fabrics.
 Wood star Zool., any one of several species of small South American humming birds belonging to the genus Calothorax. The male has a brilliant gorget of blue, purple, and other colors.
 Wood sucker Zool., the yaffle.
 Wood swallow Zool., any one of numerous species of Old World passerine birds belonging to the genus Artamus and allied genera of the family Artamidae. They are common in the East Indies, Asia, and Australia. In form and habits they resemble swallows, but in structure they resemble shrikes. They are usually black above and white beneath.
 Wood tapper Zool., any woodpecker.
 Wood tar. See under Tar.
 Wood thrush, Zool. (a) An American thrush (Turdus mustelinus) noted for the sweetness of its song.  See under Thrush. (b) The missel thrush.
 Wood tick. See in Vocabulary.
 Wood tin. Min.. See Cassiterite.
 Wood titmouse Zool., the goldcgest.
 Wood tortoise Zool., the sculptured tortoise.  See under Sculptured.
 Wood vine Bot., the white bryony.
 Wood vinegar. See Wood acid, above.
 Wood warbler. Zool. (a) Any one of numerous species of American warblers of the genus Dendroica.  See Warbler. (b) A European warbler (Phylloscopus sibilatrix); -- called also green wren, wood wren, and yellow wren.
 Wood worm Zool., a larva that bores in wood; a wood borer.
 Wood wren. Zool. (a) The wood warbler. (b) The willow warbler.