Definition of "off guard" []

• Not vigilant; unprepared; inattentive. (adjective)
• Unexpectedly or by surprise (adverb)

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• "          Walznik was still absorbing “our friend” and was caught off guard by the sudden switch to Polish."
• "Hunched over her handle bars, the Hawaiian sun beating down on her back, she was caught off guard by a strong side gust."
• "And again, when you catch a fellow off guard who seemed all right the first time, you may find that he deaconed himself for your benefit, and that all the big strawberries were on top."