defunct (adj) - no longer existing or in use; inactive, extinct, or obsolete [dih-fuhngkt]
BREAKDOWN: DE- (off) + FUNCT- (perform)
defunct can be used as a noun to refer to someone or something no longer living or in use
See also: perfunctory
“I'm inclined to think we are all ghosts-every one of us. It's not just what we inherit from our mothers and fathers that haunts us. Its all kinds of old defunct theories, all sorts of old defunct beliefs, and things like that.” —Henrik Ibsen