In professional wrestling, a hardcore match is a match in which there basically are no used--foreign objects are legal, other wrestlers may interfere, and pinfalls may be counted anywhere instead of just in the ring.  No disqualifications, no countouts, no penalties for dropping a forklift on your opponent (it's happened).

Hardcore matches have been called tons of different things--all equally silly:
 


...and hundreds of others all mean the same thing, regardless of the silly distinctions promotions try to give them.  For example, when a main event match in the World Wrestling Federation is hardcore, it is usually advertised as a "Street Fight".  When a regular match is hardcore, though, it's just a "Hardcore Match".  This is, I guess, to give the impression that a "Street Fight" is more special than a "Hardcore Match," even though they're exactly the same thing.