字面意思可以这么理解。但是它却有另一种含义！ birth 出生；birthday 出生那天；人出生时是什么都不穿，所以，in one's birthday suit是裸体，赤身裸体的意思。 例：I guess he didn’t know I was in the house. When I walked into the living room, he was just standing in his birthday suit. 我猜他当时并不知道我在屋里。我走进起居室时，他正一丝不挂地站在那儿!