Definition of on guard against
- We need to be on guard against attack.
: one assigned to protect or oversee another: such as
: a person or a body of persons on sentinel duty
: troops attached to the person of the sovereign
: to protect an edge of with an ornamental border
: to protect from danger especially by watchful attention : make secure
: to stand at the entrance of as if on guard or as a barrier
: in opposition or hostility to
: not in conformity with : contrary to
: in competition with
: in preparation for the time when
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