Kidult

A kidult is a middle aged person who enjoys being a part of youth culture and doing and/or buying things that are usually thought more suitable for children. The word is a portmanteau of kid and adult.The term was first used by Jim Ward-Nichols on the campus of Stevens Institute of Technology in Hoboken, NJ in late 1980 and is believed to have first appeared, in print, in The New York Times on August 11, 1985 in an article by Peter Martin: And in the background, on a much less lavish scale, is LBS Communications, which doesn't own its own stations but provides a lucrative stream of kidult — children, teenager and young adult — programming to independents.
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another term dreamt up by the ad agencies; its adults that use children and young adult products e.g. adults reading comics or playing starwars.