From Longman Dictionary of Contemporary Englishopen-neckedˌopen-ˈnecked adjective DCCFASTEN/DO UPan open-necked shirt is worn with the top button undone
Examples from the Corpus
open-necked• He wore an open-necked checked shirt, and jeans, and occasionally reached for the pint of lager at his side.• As she was talking a man in olive-drab slacks and an open-necked flannel shirt joined her.• The swine looked even more attractive than ever in a black open-necked polo shirt and black jeans.• Then Miguel himself came round the corner of the villa, dressed in a white open-necked shirt and dark fitted trousers.• He was wearing shorts and an open-necked shirt, and his limbs were firm with muscle and suntanned.• Another table was hidden by a group of young men in open-necked shirts and brown pullovers.• Jenkins entered, followed by two Arabs in jeans and open-necked shirts.• Often worn with pale, open-necked sports shirts and dodgy cravats. 