An phenomenon commonly seen on forums where two members will endlessly smash message after message back and forth, in the hope that they will get the last word, thus supposedly proving their point.
The rest of the forum usually loathes these tireless rebutters, for their obstinance and lack of a life. Forum tennis is best avoided by fully expressing your point of view clearly in a handful of messages at most, and then leaving it at that.
Athyy69: No, mine is. Prove yours is.
JFreek420: My team is clearly better. You prove they're not!
Athyy69: I'm not the one making the claim. You prove it!
20 pages later
Athyy69: I think I've clearly shown how wrong you are.
Admin: STFU, both of you. I'm sick of this pathetic forum tennis. Thread LOCKED.