The phrase "off-guard" typically refers to a state of being caught unaware or unprepared. Synonyms for this term include "unprepared," "unwary," "vulnerable," "defenseless," "unguarded," "careless," and "reckless." Other similar words or phrases might include "caught off guard," "surprised," "caught by surprise," "unprepared for," "taken aback," or "caught unawares." Whether in the context of a surprise attack or simply being caught off guard in a social situation, it's important to be aware of these synonyms and use them appropriately to accurately convey the intended meaning or emotion.