Basically a rifle designed to shoot a pistol cartridge.
But you really dont want to shoot that cartridge in a pistol.
Why not? I love my 30 carbine Ruger Blackhawk revolver, and I'd love to have one of the old AMT Automag III semi auto .30 carbine pistols. They are 100+ yard handguns.
Some people DO complain that they are too loud, but that doesn't bother me, and my reloads are much quieter than factory mil spec ammo, with the same performance.
Which pistols, besides the single action Ruger chambered the 30 carbine?