as dumb as an ox字面意思像公牛一样地沉默，引申为沉默不语。

【例句】
Mr.B seems as dumb as an ox, but in fact he is not.
先生看来似乎沉默不语，但他并非如此。

He was as dumb as an ox in the meeting.
开会时他沉默不语。