lower one's guard

lower one's guard (third-person singular simple present lowers one's guard, present participle lowering one's guard, simple past and past participle lowered one's guard)

1. To become less guarded; to allow oneself to become more vulnerable.

   Synonyms: drop one's guard, let one's guard down

   Antonym: keep one's guard up

• “drop lower your guard”, in Cambridge English Dictionary, Cambridge, Cambridgeshire: Cambridge University Press, 1999–present.
• “lower drop your guard let your guard down”, in Collins English Dictionary.
• “drop lower let down your guard” (US) / “drop lower let down your guard” (UK) in Macmillan English Dictionary.