adversary

n. rival; enemy; opponent; person who opposes

Adversary may refer to: In religionSatan, whose name means adversary in the Hebrew language.In computer science:Adversary (cryptography), malicious entity in cryptography whose aim is to prevent the users of the cryptosystem from achieving their goal.Adversary (online algorithm), the adversary model is used in online algorithms in order to show competitiveness of randomized algorithms.In fiction:Adversary (comics), villain from the Marvel comics universeThe Adversary, the main villain in the Fables comic book series"The Adversary" (DS9 episode), the season finale of Star Trek: Deep Space Nine's third season
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Noun
1. someone who offers opposition
(synonym) antagonist, opponent, opposer, resister
(hypernym) person, individual, someone, somebody, mortal, human, soul
(hyponym) dueler, dueller, duelist, duellist

(n.)
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.
  

(a.)
Opposed; opposite; adverse; antagonistic.
  

(a.)
Having an opposing party; not unopposed; as, an adversary suit.
  

Satan [from Hebrew satan adversary, opposer from the verbal root satan to lie in wait, oppose, be an adversary; or possibly from the verbal root shut to whip, scourge, run hither and thither on errands; Greek satan, satanas] Adversary; with the definite article (has-satan) the adversary in the Christian sense, as the Devil. This Satan of the exoteric Jewish and Christian books is a mere figment of the monkish theological imagination. From the second possible derivation many eminent Shemitic scholars have held that the Satan of the Book of Job was a good angel arranged by God to try the characters of men in order to help them; and therefore supposedly to be different from the Satan of other books of the Bible. The theosophist would not limit the good angel to the Book of Job alone, but would look upon the adversative or contrary forces of nature as being the means upon which each one tries his will, resolution, and determination to evolve and grow spiritually and intellectually. The Satan of this hypothesis is in a sense our own lower character combined with the lower forces of nature surrounding earth and elsewhere.