be on guard(redirected from be on her guard)
be on (one's) guard
To be especially careful or vigilant; to be prepared for danger or surprises. He's got a lot of tricky moves, so be on your guard! Those trails can be a bit treacherous to climb. I just hope she's on her guard.
be on guard
To be very attentive and alert, so as to avoid danger in a particular situation. A possessive adjective can be used between "on" and "guard." When you're in the big city, you need to be on guard against criminals. I'm on my guard because I know the older guys on the team are going to prank me. I hope she's on her guard. Those trails can be a bit treacherous to climb.
Farlex Dictionary of Idioms. © 2022 Farlex, Inc, all rights reserved.