opt-inWiktionary 原文英/ˈɒptˌɪn/美/ˈɑptˌɪn/构词拆解opt词干+in词干词源说明From opt + in.释义形容词adjective1The property of having to choose explicitly to join or permit something; a decision having the default option being exclusion or avoidance; used particularly with regard to mailing lists and advertising.同族词派生词 1double opt-in