guard
n. countablen. a person whose job is to protect a place or keep people safe. It can also be a piece of equipment that covers a dangerous part of a machine.
n. a person or group assigned to protect a location, person, or object from danger or unauthorized access. Also refers to a protective device or shield designed to prevent injury or damage.
The security guard checks everyone's ID at the entrance.
The museum hired an extra guard to stand near the famous painting during the busy holiday weekend.
Engineers installed a heavy steel guard over the rotating gears to ensure that no loose clothing could become entangled in the machinery during operation.
From Middle English garde, from early Middle French or late Old French guarde (“a guardian, warden, keeper”) (whence modern French garde), from the verb guarder. Doublet of garda, which is from Irish.
From early Middle French garder or late Old French (circa 14th cent) guarder (“to keep, ward, guard, save, preserve, etc.”), from Early Medieval Latin wardo, from Frankish wardēn, from Proto-Germanic wardāną (“to guard, protect”). Cognate with French garder, Old English weardian (whence also the English inherited doublet ward). See also English regard.
Often used in the phrase 'on guard' to describe a state of alertness.