clam up
保持沉默或拒绝说话
口语·表示因紧张或秘密而沉默
英文释义
to become silent or refuse to talk, usually due to shyness, nervousness, or a desire to keep a secret
例句
Whenever the teacher asked him a question, he would clam up and refuse to answer.
典故来源
源自蛤蜊遇到危险时会紧闭外壳，比喻人突然沉默不语。