Rud·der n.
 1. Naut. The mechanical appliance by means of which a vessel is guided or steered when in motion. It is a broad and flat blade made of wood or iron, with a long shank, and is fastened in an upright position, usually by one edge, to the sternpost of the vessel in such a way that it can be turned from side to side in the water by means of a tiller, wheel, or other attachment.
 2. Fig.: That which resembles a rudder as a guide or governor; that which guides or governs the course.
    For rhyme the rudder is of verses.   --Hudibras.
 3. In an aircraft, a surface the function of which is to exert a turning moment about an axis of the craft.
 Balance rudder Naut., a rudder pivoted near the middle instead of at the edge, -- common on sharpies.
 Drop rudder Naut., a rudder extending below the keel so as to be more effective in steering.
 Rudder chain Naut., one of the loose chains or ropes which fasten the rudder to the quarters to prevent its loss in case it gets unshipped, and for operating it in case the tiller or the wheel is broken.
 Rudder coat Naut., a covering of tarred canvas used to prevent water from entering the rudderhole.
 Rudder fish. Zool. (a) The pilot fish. (b) The amber fish (Seriola zonata), which is bluish having six broad black bands. (c) A plain greenish black American fish (Leirus perciformis); -- called also black rudder fish, logfish, and barrel fish. The name is also applied to other fishes which follow vessels.
 Rudder pendants Naut., ropes connected with the rudder chains.

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