be+on+guard
51guard — I (guardian) noun bodyguard, custodian, defender, defense, keeper, monitor, palladium, panoply, peace officer, protector, security, sentinel, sentry, surveillance, ward, warden, watchman II (safeguard) noun palladium, protection, protector,… …
52guard against — index anticipate (expect) Burton s Legal Thesaurus. William C. Burton. 2006 …
53guard's van — n BrE the part of a train where the person in charge of it travels American Equivalent: caboose …
54guard rail — guard ,rail noun count a bar or fence put for safety at the edge of something such as a road, a bridge, or stairs …
55guard — vb shield, protect, safeguard, *defend Analogous words: watch, attend, *tend, mind: convoy, escort, chaperon, conduct, *accompany …
56guard cell — guard′ cell n. bot either of a pair of crescent shaped cells that flank each plant pore and control its opening and closing by means of turgidity …
57guard duty — guard′ du ty n. mil a military assignment involving watching over or protecting a person or place or supervising prisoners …
58guard hair — guard′ hair n. zool. the long, usu. stiff outer hair protecting the underfur in certain animals …
59guard cell — n. either of the two bean shaped cells which surround and control a stoma, or air pore, in the epidermis of a plant …
60guard hair — n. any of the coarse protective hairs in the outer fur of certain mammals …