-somethings1) COMB in ADJ -something is combined with numbers such as twenty and thirty to form adjectives which indicate an approximate amount, especially someone's age. For example, if you say that someone is thirty-something, you mean they are between thirty and forty years old.2) COMB in N-COUNT People of a similar age range are sometimes referred to as, for example, twenty-somethings or thirty-somethings. [JOURNALISM]
Most American twenty-somethings do not read about politics.
English dictionary. 2008.