Guard  —v. 1 (often foll. By from, against) watch over and defend or protect. 2 keep watch by (a door etc.) To control entry or exit. 3 supervise (prisoners etc.) And prevent from escaping. 4 keep (thoughts or speech) in check. 5 (foll. By against) take precautions. —n. 1 state of vigilance. 2 person who protects or keeps watch. 3 soldiers etc. Protecting a place or person; escort. 4 official in general charge of a train. 5 part of an army detached for some purpose (advance guard). 6 (in pl.) (usu. Guards) body of troops nominally employed to guard a monarch. 7 thing that protects (fire-guard). 8 us prison warder. 9 defensive posture or motion in boxing etc.  be on (or keep or stand) guard keep watch. Off (or off one's) guard unprepared for some surprise or difficulty. On (or on one's) guard prepared for all contingencies. [germanic: related to *ward]