Maybe in the uk you could call it a shump but here in the good ole' USA it's a vertical shooter.
Shumps are gun games from the first or third person perspective. (Like T2 or hogan's alley) Games in which you pilot a ship/dragon/whatever that has a gun mounted to it are either horizonal or vertical shooters.
Just my opinion, but I think it's in the majority.
It's kinda like all fighter games. Only versus games (like street fighter) are fighters, the side scrolling games like tmnt are beat em ups. It urks me to no end when someone calls tmnt a fighter game.
