twentysomething /ˈtwɛn.tiː.ˌsʌm.θɪŋ/adjective 1noun 1number 1forms 1 adjective1 •Aged between twenty and thirty.You may feel as inexperienced as a twentysomething woman just starting out, but it’s not too late to make changes. — 1993 noun1 •(informal) A person whose age is between twenty and twenty-nine years, inclusive; someone in their twenties.This is the twentysomething generation, those 48 million young Americans ages 18 through 29 who fall between the famous baby boomers and the boomlet of children the baby boomers are producing. — 1990 number1 •Between twenty and thirty. formstwentysomethings