出处：按学科分类—语言、文字 中国对外翻译出版公司《汉英成语词典》第273页（267字）
指动作快的人最先得到的意思，例游泳学习班名额有限，你应尽早去报名，否则别人就捷足先登了。
If you want to join the swimming class，you must sign up as soon as possible．You know there are only a few vacancies and the person who signs up first will be the lucky one．