A classic example:
In the opening scene of Richard II, Henry Bolingbroke and Mowbray seeks the adjudication of the king. They hurl accusations of treachery and cowardliness at each other. They engage in what we call in colloquial English 'trash-talk' without an actual fight of swords (they do later, but that is not the point). What formal/literary word can we use in describing that sort of 'trash-talk'?