Adversary

n. pl. Adversaries ().
  1. One who is turned against another or others with a design to oppose or resist them; a member of an opposing or hostile party; an opponent; an antagonist; an enemy; a foe.
  2. The Adversary ,
    The Satan, or the Devil.

a.
  1. Opposed; opposite; adverse; antagonistic.
  2. (Law) Having an opposing party; not unopposed; as, an adversary suit.