Source : Webster's Revised Unabridged Dictionary (1913)

Adversary \Ad`ver*sa*ry\, n.; pl. {Adversaries}. [OE.
   adversarie, direct fr. the Latin, and adversaire, fr. OF.
   adversier, aversier, fr. L. adversarius (a.) turned toward,
   (n.) an adversary. See {Adverse}.]
   One who is turned against another or others with a design to
   oppose