catch (one) off guard

catch (one) off guard

To engage, take advantage of, or seize upon one when one is not especially careful, vigilant, or prepared for danger or surprises. He's got a lot of tricky moves, so make sure he doesn't catch you off guard! The soldiers moved in quickly, hoping to catch the enemy troops off guard. I think I caught him off guard when I told him I was resigning.
See also: catch, guard, off
Farlex Dictionary of Idioms.

catch someone off guard

 and catch one off (one's) guard
Fig. to catch a person at a time of carelessness. Tom caught Ann off guard and frightened her. She caught me off my guard, and my hesitation told her I was lying.
See also: catch, guard, off

catch one off

(one's) guard Go to catch someone off guard.
See also: catch, off, one
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs.

catch off guard

see under off guard.
See also: catch, guard, off
The American Heritage® Dictionary of Idioms by Christine Ammer.

catch someone off guard

or

take someone off guard

COMMON If something catches you off guard or takes you off guard, it happens unexpectedly and you are not prepared to respond to it. Note: Your guard is the position that you get in when you are ready to defend yourself in sports such as boxing or fencing. I didn't know how to answer him. The question caught me off guard. I wasn't expecting him to pass the ball to me and it took me off guard.
See also: catch, guard, off, someone
Collins COBUILD Idioms Dictionary, 3rd ed.

catch somebody off (their) ˈguard

happen when somebody is not prepared: The question caught him off his guard and he couldn’t answer. Businesses were caught off guard by the sudden rise in interest rates.
See also: catch, guard, off, somebody
Farlex Partner Idioms Dictionary
See also:
  • 1FTR
  • drive (one) out of office
  • force (one) out of office
  • force out of office
  • give (one) (one's) head
  • give head
  • give somebody their head
  • give someone their head
  • deep water
  • cooking for one