ADJECTIVE (3)

1. (used of persons or the military) characterized by having or bearing arms;
- Example: "armed robbery"

2. having arms or arms as specified; used especially in combination;
- Example: "the many-armed goddess Shiva"

3. (used of plants and animals) furnished with bristles and thorns;

The Collaborative International Dictionary of English v.0.48:

Arm \Arm\, v. t. [imp. & p. p. Armed; p. pr. & vb. n.
   Arming.] [OE. armen, F. armer, fr. L. armare, fr. arma,
   pl., arms. See arms.]
   1. To take by the arm; to take up in one's arms. [Obs.]
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            And make him with our pikes and partisans
            A grave: come, arm him.               --Shak.
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            Arm your prize;
            I know you will not lose him.         --Two N. Kins.
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   2. To furnish with arms or limbs. [R.]
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            His shoulders broad and strong,
            Armed long and round.                 --Beau. & Fl.
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   3. To furnish or equip with weapons of offense or defense;
      as, to arm soldiers; to arm the country.
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            Abram . . . armed his trained servants. --Gen. xiv.
                                                  14.
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   4. To cover or furnish with a plate, or with whatever will
      add strength, force, security, or efficiency; as, to arm
      the hit of a sword; to arm a hook in angling.
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   5. Fig.: To furnish with means of defense; to prepare for
      resistance; to fortify, in a moral sense.
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            Arm yourselves . . . with the same mind. --1 Pet.
                                                  iv. 1.
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   To arm a magnet, to fit it with an armature.
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The Collaborative International Dictionary of English v.0.48:

Armed \Armed\, a.
   1. Furnished with weapons of offense or defense; furnished
      with the means of security or protection. "And armed
      host." --Dryden.
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   2. Furnished with whatever serves to add strength, force, or
      efficiency.
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            A distemper eminently armed from heaven. --De Foe.
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   3. (Her.) Having horns, beak, talons, etc; -- said of beasts
      and birds of prey.
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   Armed at all points (Blazoning), completely incased in
      armor, sometimes described as armed cap-[`a]-pie.
      --Cussans.

   Armed en flute. (Naut.) See under Flute.

   Armed magnet, a magnet provided with an armature.

   Armed neutrality. See under Neutrality.
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WordNet (r) 3.0 (2006):

armed
    adj 1: (used of persons or the military) characterized by having
           or bearing arms; "armed robbery" [ant: unarmed]
    2: having arms or arms as specified; used especially in
       combination; "the many-armed goddess Shiva" [ant: armless]
    3: (used of plants and animals) furnished with bristles and
       thorns [ant: unarmed]