sap

Concise Oxford English Dictionary © 2008 Oxford University Press:
sap1

▶noun

• 1 the fluid, chiefly water with dissolved sugars and mineral salts, circulating in the vascular system of a plant.

• 2 vigour or energy.

▶verb (saps, sapping, sapped) gradually weaken (a person's strength or power).

■ (sap someone of) drain someone of (strength or power).

– derivatives
sapless adjective.

– origin OE sæp, prob. of Gmc origin; the verb is derived orig. from the verb sap2, in the sense ‘undermine’.

Concise Oxford English Dictionary © 2008 Oxford University Press:
sap2

▶noun historical a tunnel or trench to conceal an assailant's approach to a fortified place. ▶verb (saps, sapping, sapped)

• 1 historical dig a sap.

• 2 archaic make insecure by removing the foundations.

• 3 (often as noun sapping) Geography undercut by water or glacial action.

– origin C16: from Fr. saper, from Ital. zappare, from zappa ‘spade, spadework’, prob. from Arab. sarab ‘underground passage’, or sabora ‘probe a wound, explore’.

Concise Oxford English Dictionary © 2008 Oxford University Press:
sap3

▶noun informal, chiefly N. Amer. a foolish person.

– origin C19: abbrev. of dial. sapskull ‘person with a head like sapwood’.

Concise Oxford English Dictionary © 2008 Oxford University Press:
sap4 US informal, dated

▶noun a bludgeon or club. ▶verb (saps, sapping, sapped) hit with a sap.

– origin C19: abbrev. of sapling.