The Collaborative International Dictionary of English v.0.48:

Armor \Ar"mor\, n. [OE. armure, fr. F. armure, OF. armeure, fr.
   L. armatura. See Armature.] [Spelt also armour.]
   1. Defensive arms for the body; any clothing or covering worn
      to protect one's person in battle.
      [1913 Webster]

   Note: In English statues, armor is used for the whole
         apparatus of war, including offensive as well as
         defensive arms. The statues of armor directed what arms
         every man should provide.
         [1913 Webster]

   2. Steel or iron covering, whether of ships or forts,
      protecting them from the fire of artillery.
      [1913 Webster]

   Coat armor, the escutcheon of a person or family, with its
      several charges and other furniture, as mantling, crest,
      supporters, motto, etc.

   Submarine, a water-tight dress or covering for a diver. See
      under Submarine.
      [1913 Webster]

WordNet (r) 3.0 (2006):

armor
    n 1: protective covering made of metal and used in combat [syn:
         armor, armour]
    2: a military unit consisting of armored fighting vehicles [syn:
       armor, armour]
    3: tough more-or-less rigid protective covering of an animal or
       plant [syn: armor, armour]
    v 1: equip with armor [syn: armor, armour]

Moby Thesaurus II by Grady Ward, 1.0:

85 Moby Thesaurus words for "armor":
   Philistinism, aegis, armament, armature, armor plate, bard, beaver,
   body armor, brassard, breastplate, buckler, bulletproof vest,
   callosity, callousness, callus, chain armor, chain mail, chitin,
   cloak, coat of mail, coif, corselet, cortex, cover, cuirass,
   elytron, episperm, flintiness, formidable defenses, gas mask,
   gauntlet, guard, habergeon, hard heart, hard shell, hardenedness,
   hardheartedness, hardness, hardness of heart, harness, hauberk,
   headpiece, heart of stone, helm, helmet, imperviousness,
   induration, insensitiveness, insensitivity, inuredness, jamb,
   lorica, lorication, mail, mantle, nasal, needles, obduracy,
   obdurateness, panoply, pericarp, plate, plate armor, protection,
   protective covering, rhinoceros hide, rondel, safeguard, screen,
   scute, scutum, security, shell, shelter, shield, shroud, spines,
   stoniness, suit of armor, test, testa, thick skin, veil, visor,
   ward



The Devil's Dictionary (1881-1906):

ARMOR, n.  The kind of clothing worn by a man whose tailor is a
blacksmith.