{adj.} In a careless attitude; not alert to coming danger; not watching. * /In the second that the boxer was off guard, his opponent landed a knockout punch./ * /Timmy s question caught Jean off guard, and she told him the secret before she knew it./ Contrast: ON GUARD.
OFF GUARD
Meaning of OFF GUARD in English
Dictionary of English idioms . Словарь английских идиом. 2012