Definition
To remain completely silent; to not utter a word.
指完全不说话，保持沉默。
When asked about the issue, he didn't say boo.
当被问及这个问题时，他一句话也没说。
She didn't say boo during the meeting, just listened quietly.
她在会议上一句话也没说，只是静静地听着。
He didn't say boo all evening, as if he was sulking.
他整晚一句话也没说，好像在生闷气。
To be very timid and easily frightened; to be excessively nervous.
形容胆小容惊
The little boy is so timid that he doesn’t say boo when he sees even the slightest movement.
这个小男孩非常胆小，看到一点动静都不会吭声。
She is very nervous and doesn't say boo when she is in public.
她非常紧张，在公共场合都不敢吭声。
I know someone who is so afraid that she doesn't say boo when facing any problem.
我认识一个人，她非常害怕，面对任何问题都不敢吭声。