The acto of "owning" "destroying" "completely mangling" the enemy. Usually used in online multiplayer games, is often tagged to real life though.
That was some pretty awesome tankage when you lobbed that grenade at those grunts.
Holy shit that was some extreme tankage you put on that warthog.
Robbie runs into Robert, whacks straight off him and hits the ground with a loud thud and goes owwwwwwww. Thats tankage