From Longman Dictionary of Contemporary Englishold lagˌold ˈlag noun [countable] British English old-fashioned SCCSCJsomeone who has been in prison many times
Examples from the Corpus
old lag• Political loony, surprised thief, old lag with a grudge ... it's facts I want, not surmise.Origin old lag (1800-1900) lag “to send to prison” ((1800-1900)) 