Source : Webster's Revised Unabridged Dictionary (1913)

Sap \Sap\, n. [AS. s[ae]p; akin to OHG. saf, G. saft, Icel.
   safi; of uncertain origin; possibly akin to L. sapere to
   taste, to be wise, sapa must or new wine boiled thick. Cf.
   {Sapid}, {Sapient}.]
   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} (Zo["o]l.), any one of several species of small
      American woodpeckers of the genus {Sphyrapicus},
      especially the yellow-bellied woodpecker ({S. 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.