Be my guest: A set phrase encouraging or allowing someone else to take action; Help yourself.; After you. (A polite way of indicating that someone else should go first, help himself or herself to something, or take the last one of something.); (informal) used to give somebody permission to do something that they have asked to do; Go ahead, do or take what you asked for. This casual expression, current since about 1950, generally is a response to a request for something trivial.
中文释义：在英美人士的日常口语中，be my guest 常用作请便，别客气的意思。通常当别人问你可以不可以怎么样，征询你的同意时，be my guest就是比较客气的回答。例句：-Can I use your umbrella? -Be my guest.（-我可以用一下你的伞吗？-请便，不要客气。）在美国俚语中be my guest还有具有讽刺含义的用法，通常翻译为悉听尊便，随便你。例句：You want to tell cop he’s wrong? Be my guest.（你想告诉警察他错了吗？悉听尊便。）