Definition of "fad"

You're a fad, that means you're something that we've already had, but once you're gone, you don't come back.

2004, Andre R. Young, “Encore”, in Encore

The pet rock fad was started by an advertising executive named Gary Dahl. The premise was simple: take ordinary rocks, glue eyes on them, and market them as pets.

2010, Eric J. Cesal, Down Detour Road: An Architect in Search of Practice, page 134