The Collaborative International Dictionary of English v.0.48:

Enemy \En"e*my\, n.; pl. Enemies. [OF. enemi, F. ennemi, from
   L. inimicus; in- (negative) + amicus friend. See Amicable.]
   One hostile to another; one who hates, and desires or
   attempts the injury of, another; a foe; an adversary; as, an
   enemy of or to a person; an enemy to truth, or to falsehood.
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         To all good he enemy was still.          --Spenser.
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         I say unto you, Love your enemies.       --Matt. v. 44.
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   The enemy (Mil.), the hostile force. In this sense it is
      construed with the verb and pronoun either in the singular
      or the plural, but more commonly in the singular; as, we
      have met the enemy and he is ours or they are ours.
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            It was difficult in such a country to track the
            enemy. It was impossible to drive him to bay.
                                                  --Macaulay.

   Syn: Foe; antagonist; opponent. See Adversary.
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The Collaborative International Dictionary of English v.0.48:

Enemy \En"e*my\, a.
   Hostile; inimical. [Obs.]
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         They . . . every day grow more enemy to God. --Jer.
                                                  Taylor.
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WordNet (r) 3.0 (2006):

enemy
    n 1: an opposing military force; "the enemy attacked at dawn"
    2: an armed adversary (especially a member of an opposing
       military force); "a soldier must be prepared to kill his
       enemies" [syn: enemy, foe, foeman, opposition]
    3: any hostile group of people; "he viewed lawyers as the real
       enemy"
    4: a personal enemy; "they had been political foes for years"
       [syn: foe, enemy] [ant: ally, friend]