this neologism stems from the seminal hip-hop release deltron 3030 by the group of the same name (dan the automator, del tha funkee homosapien, kid koala), specifically track 3, "the
fantabulous rap
extravaganza."
usage: instupituous refers to something that is beyond dope, possibly interspatial, maybe boasting jet propulsion or at least better rhymes than any you've ever heard, including the time your cousin d-pennyweight busted freestyles for an hour and a half while you and your girl jammed to it by a bonfire
on the beach out of the back of a 1967 chevy nova.