Sap n.
 1. The juice of plants of any kind, especially the ascending and descending juices or circulating fluid essential to nutrition.
 Note: ☞ The ascending is the crude sap, the assimilation of which takes place in the leaves, when it becomes the elaborated sap suited to the growth of the plant.
 2. The sapwood, or alburnum, of a tree.
 3. A simpleton; a saphead; a milksop. [Slang]
 Sap ball Bot., any large fungus of the genus Polyporus. See Polyporus.
 Sap green, a dull light green pigment prepared from the juice of the ripe berries of the Rhamnus catharticus, or buckthorn. It is used especially by water-color artists.
 Sap rot, the dry rot. See under Dry.
 Sap sucker Zool., any one of several species of small American woodpeckers of the genus Sphyrapicus, especially the yellow-bellied woodpecker (Sphyrapicus varius) of the Eastern United States. They are so named because they puncture the bark of trees and feed upon the sap. The name is loosely applied to other woodpeckers.
 Sap tube Bot., a vessel that conveys sap.