off his guard

Thesaurus

Adj.

1.

off his guard - not prepared or vigilant; "the blow caught him napping"; "caught in an off-guard moment"; "found him off his guard"napping, off guard, off her guard, off one's guard, off your guard, off-guardunready - not prepared or in a state of readiness; slow to understand or respond; "she cursed her unready tongue"