catch 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

catch someone off guard

 and catch one off (one's) guardFig. 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 off guard

see under off guard. See also: catch, guard, off