From Longman Dictionary of Contemporary Englishtwentysomethingtwen‧ty‧some‧thing /ˈtwentiˌsʌmθɪŋ/ noun [countable] informal someone who is between the ages of 20 and 29 → thirtysomething A crowd of twentysomethings were gathered outside the club. —twentysomething adjective
Examples from the Corpus
twentysomething• Q, a sharp twentysomething, set the ball rolling by applying the lessons of club culture to literature. 