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]

Moby Thesaurus II by Grady Ward, 1.0:

76 Moby Thesaurus words for "armed":
   accoutered, all ready, all set, armed and ready, arrayed, battled,
   booted and spurred, briefed, bristling with arms, carrying,
   catered, cloaked, coached, cocked, copyrighted, covered, defended,
   deployed, embattled, endowed, engaged, equipped, familiarized,
   fitted, fitted out, full-armed, furnished, good and ready, groomed,
   guarded, heavy-armed, heeled, in arms, in battle array,
   in readiness, in the saddle, informed, invested, invulnerable,
   light-armed, loaded, loaded for bear, mature, mobilized,
   on the mark, outfitted, patented, planned, policed, prearranged,
   prepared, prepared and ready, prepped, primed, protected, provided,
   psyched up, purveyed, ranged, ready, ready for anything, rigged,
   ripe, safe, safeguarded, screened, set, sheltered, shielded,
   supplied, sword in hand, under arms, up in arms, vigilant,
   well-armed, well-prepared