Killer Instinct has a kind of convoluted combo system, which we'll talk about in depth another day. You can, with skill, string together lots of moves to just pummel your opponent senseless for several seconds.
Good thing, then, that there's a method to break the combos in mid-stream. A move that everyone has called, oddly enough, a 'combo breaker'. The breaker is different for each character, but it's normally just one of their regular moves done at the right time, and with the right button.
Okay, at its basic form, a combo consists of an opening move (the Opener), an autodouble (for a couple more hits), and then a finisher for a few more hits and the icing on the cake.
Problem is, though, that to break the combo you have to have timing and a pretty deep understanding of each character's moves.
Timing. You have to do your breaker during the autodouble portion of the combo (or the linker stage, but that's another pro tip). Not too tough, right? Just have to learn to recognize where the opening move ends and the next couple of hits start. Now, the 'intimate knowledge' part comes in. You have to recognize whether the autodouble was initiated with a weak, medium, or strong button, and press the corresponding button to break the combo. Weak breaks medium, medium breaks strong, and strong breaks weak.
But that's a whole lot of memorization, attentiveness, and, *gasp*, work!
Turns out that there's a slightly easier way.
On the 'Vs.' screen (that shows the matchup) press Down + Start and you'll hear this sound.
Then, the combo breakers get way easier. Now you can do them with any strength button you want. Though you still have to get the timing down.
But once you get that down, you're in great shape.
Oh, and it works in the arcade version, too.