'Adversary' in the Bible

And her adversary provoked her much also, to make her fret, because Jehovah had shut up her womb.

But the princes of the Philistines were wroth with him; and the princes of the Philistines said to him, Make the man return, that he may go again to his place where thou hast appointed him, that he go not down with us to the battle, that in the battle he be not an adversary to us; for wherewith should this fellow reconcile himself to his master? should it not be with the heads of these men?