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):

armour
    n 1: a military unit consisting of armored fighting vehicles
         [syn: armor, armour]
    2: protective covering made of metal and used in combat [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]