-in/ɪn; ɪn/ (forming compound ns 用以构成复合名词) (becoming dated 渐旧) (added to another word (usu a v) to indicate an activity in which many people participate 附於另一词（通常为动词）後, 表示有很多人参加的活动): a `sit-in * `teach-ins.
牛津英汉双解词典