我们都知道牙齿是没有皮肤，也即 skin，那么 by the skin of one's teeth 肯定不是正常的“靠牙齿的皮肤”的意思，它是一个习惯用语，可以意为“侥幸，勉强”，寓意：
barely manage to do something勉强能做点什么 narrowly succeed in doing something勉强成功地做某事 manage to do something by the smallest margin设法以最小的差距做某事 例如： We managed to complete the project on time by the skin of our teeth.我们勉强按时完成了这个项目。
After being chased by the police a long way, the criminal managed to escape by the skin of his teeth.在被警察追了很长一段路后，罪犯侥幸逃脱了。 解析：此句是 after 引导的时间状语从句，从句的主语与主句主语一致，都是 the criminal，且从句谓语包括有动词 be 时，有时可省略从句中的主语和动词 be. He made the final cut-off list of the university by the skin of his teeth.他勉强列入了这所大学的最后一份名单。 I managed to pass the exam by the skin if my teeth.我勉强通过了考试。 解析：manage to do sth 表示设法完成或成功完成某事，通常是困难的事。
The team held on by the skin of their teeth to win the crucial match.该队勉强坚持着，赢得了这场关键的比赛。 He cleared the selection criteria by the skin of his teeth.他勉强清掉了选择标准。 We escaped the raging rioters by the skin of our teeth.我们侥幸逃脱了暴徒的袭击。 就像之前描述的那样，一个短语的意思很奇怪或是不合常理，那么它就是一个习语，跟身体其他器官有关的习语类似，例如 a dab hand，本身没任何意义，寓意“一个能手，一个高手”，又如 bite head off，本意思不合常理，寓意“大发雷霆”，等等。
