To prove or even refute by proof, particularly on threat of fight.
To engage in (battle, fight etc.).
To prove or to refute by proof; to clear (one's self).
In old English law, to show; justify; vindicate, as an assertion; clear one's self, either by proving your very own case or by refuting compared to an adversary: occasionally used of an abstract or chronologic tracing of a chain of subject to property.
To claim and try to win by fight or fight; battle for.