on one's guard

guard

O o

Definitions of on one's guard words

verb with object on one's guard to keep safe from harm or danger; protect; watch over: to guard the ruler. 1
verb with object on one's guard to keep under close watch in order to prevent escape, misconduct, etc.: to guard a prisoner. 1
verb with object on one's guard to keep under control or restraint as a matter of caution or prudence: to guard one's temper. 1
verb with object on one's guard to provide or equip with some safeguard or protective appliance, as to prevent loss, injury, etc. 1
verb with object on one's guard Sports. to position oneself so as to obstruct or impede the movement or progress of (an opponent on offense): The linebacker moved to his right to guard the end going out for a pass. 1
verb with object on one's guard Chess. to protect (a piece or a square) by placing a piece in a supportive or defensive position relative to it. 1

before 1375

One of the 22% oldest English words

1375-1425; late Middle English garde guardianship < Old French g(u)arde, noun derivative of g(u)arder (v.) < Germanic; see ward

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adjective

verb

adverb

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preposition

conjunction

determiner

exclamation

A common word. It’s meaning is known to most children of preschool age. About 98% of English native speakers know the meaning and use the word.

Most Europeans know this English word. The frequency of it’s usage is somewhere between "mom" and "screwdriver".