Used in off-road or other vehicle modification subcultures.
Usage:
(1)Usually referring to a vehicle that is heavily modified as a sarcastic comment, or (2) a lightly modified vehicle as a genuine statement
That car with the fart cannon is pretty cool but it's still stockish.
"I'd say you have a cool jeep but it looks stockish" (pan to said jeep with huge tires, one ton axles, regeared and locked differentials, possible engine swap, chromoly everything)