n. The juice or fluid which circulates in all plants, being as indispensable to vegetable life as is the blood to animal life.n. Hence The juice or fluid the presence of which in anything is characteristic of a healthy, fresh, or vigorous condition; blood.n. The alburnum of a tree; the exterior part of the wood, next to the bark; sap-wood.n. Same as saphead.To act like a sap; play the part of a ninny or a soft fellow.n. A tool for digging; a mattock.n. [⟨ sap, verb] Milit., a narrow ditch or trench by which approach is made to a fortress or besieged place when within range of fire.To undermine; render unstable by digging into or eating away the foundations, or, figuratively, by some analogous insidious or invisible process; impair the stability of, by insidious means: as, to sap a wall; to sap a person's constitution, or the morals of a community.Milit., to approach or pierce with saps or trenches.To dig or use saps or trenches; hence, to impair stability by insidious means.n. In archery, the light-colored portion of a bowstaff composed of the sap-wood. This portion forms the back of a self-bow.n. A quarryman's name for rock which is partially decayed and which exhibits this quality by iron stains and other discolorations. It is usually thrown away.