"咬嘴唇"在英语中叫做 "biting one's pp."
这个短语最早起源于古英语，表示因紧张、不安或痛苦而咬紧嘴唇的动作。在现代英语中，它还可以用来描述一个人在思考或思索时的表情。
例句：
"She bit her pp nervously as she waited for the results of her job interview."（她紧张地咬着嘴唇等待面试结果。）
"He bit his pp, trying to come up with a solution to the problem."（他咬着嘴唇，试图找到解决问题的办法。）
"The pttle girl bit her pp and looked down, refusing to cry in front of everyone."（小女孩咬着嘴唇，低下头，不愿在大家面前哭。）