v. & n.
v. 1 tr. (often foll. by from, against) watch over and defend or protect from harm. 2 tr. keep watch by (a door etc.) so as to control entry or exit. 3 tr. supervise (prisoners etc.) and prevent from escaping. 4 tr. provide (machinery) with a protective device. 5 tr. keep (thoughts or speech) in check. 6 tr. provide with safeguards. 7 intr. (foll. by against) take precautions. 8 tr. (in various games) protect (a piece, card, etc.) with set moves.
n. 1 a state of vigilance or watchfulness. 2 a person who protects or keeps watch. 3 a body of soldiers etc. serving to protect a place or person; an escort. 4 US a prison warder. 5 a part of an army detached for some purpose (advance guard). 6 (in pl.) (usu. Guards) any of various bodies of troops nominally employed to guard a monarch. 7 a thing that protects or defends. 8 (often in comb.) a device fitted to a machine, vehicle, weapon, etc., to prevent injury or accident to the user (fire-guard). 9 Brit. an official who rides with and is in general charge of a train. 10 in some sports: a a protective or defensive player. b a defensive posture or motion. be on (or keep or stand) guard (of a sentry etc.) keep watch. guard cell Bot. either of a pair of cells surrounding the stomata in plants. guard-rail a rail, e.g. a handrail, fitted as a support or to prevent an accident. guard ring Electronics a ring-shaped electrode used to limit the extent of an electric field, esp. in a capacitor. guard's van Brit. a coach or compartment occupied by a guard. lower one's guard reduce vigilance against attack. off (or off one's) guard unprepared for some surprise or difficulty. on (or on one's) guard prepared for all contingencies; vigilant. raise one's guard become vigilant against attack. guarder n. guardless adj.
[ ME f. OF garde, garder ult. f. WG, rel. to WARD n. ]