From Longman Dictionary of Contemporary Englishround-shoulderedˌround-ˈshouldered adjective HBHsomeone who is round-shouldered has shoulders that are bent forwards or slope downwards
Examples from the Corpus
round-shouldered• If you stoop or are round-shouldered these shoulder movements will help to rectify this problem area for you.• Joseph, always referred to and called Jossey Dummy, was a tall, thin, round-shouldered youth. 