I think "disc shaped" and "torpedo shaped". are common terms you're looking for. With disc shaped, or plate shaped, being fish like piranha, discus, silver dollars, tetras, etc. I've also heard high bodied fish. Torpedo shaped fish would be more like minnows, neons, convict cichlids, etc.
That said, there are plenty of fish that don't fit either category. Oscars I'd put right in the middle of the two.