This phrase is generally used in message boards to break up a string of similar or continuous posts.
It is derived from the game Killer Instinct.
Anon: C-C-C-C-Combo breaker!
2. A message used to break a string of posts with similar subject matter.
The word originates from the fighting game Killer Instinct, where it is announced whenever a combo is broken.
Guy1: post 2
Guy1: post 3
Guy1: this is fun
Guy1: blah :)
Guy1: 490 posts to go.
random person: C-C-C-C-Combo breaker!
Guy1: damn! >.<
random person: lolz
person1: Hi all
person1: C-C-C-C-Combo breaker!