I picked up a word I didn't know from a Pharyngula commenter.
From Merriam-Webster:
flyting: a dispute or exchange of personal abuse in verse form.
From Wikipedia:
In Norse and Germanic cultures, flyting is a contest of insults, either as a prelude to battle or as a form of combat in its own right. The exchange is regular, if not ritualized, and the insults usually center on accusations of cowardice or sexual impropriety or perversion.
I like the word. It reminds me of old limerick battles.