1.When a person gets "chump"(ed).
2. What a person says (in a higher pitched voice) when he or she witnesses a person get "chump"(ed).
3. When someone completely insults the shit out of someone who set himself up for it or deserves it.
John: Well I don't know Tim, why don't you take a shower and lose some weight you fuckin' disgusting-ass abhorence to society?!
Billy: Chump City!