The Collaborative International Dictionary of English v.0.48:

Supporter \Sup*port"er\, n.
   1. One who, or that which, supports; as, oxygen is a
      supporter of life.
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            The sockets and supporters of flowers are figured.
                                                  --Bacon.
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            The saints have a . . . supporter in all their
            miseries.                             --South.
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   2. Especially, an adherent; one who sustains, advocates, and
      defends; as, the supporter of a party, faction, or
      candidate.
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   3. (Shipbuilding) A knee placed under the cathead.
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   4. (Her.) A figure, sometimes of a man, but commonly of some
      animal, placed on either side of an escutcheon, and
      exterior to it. Usually, both supporters of an escutcheon
      are similar figures.
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   5. (Med.) A broad band or truss for supporting the abdomen or
      some other part or organ.
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WordNet (r) 3.0 (2006):

supporter
    n 1: a person who backs a politician or a team etc.; "all their
         supporters came out for the game"; "they are friends of the
         library" [syn: supporter, protagonist, champion,
         admirer, booster, friend]
    2: someone who supports or champions something [syn: patron,
       sponsor, supporter]
    3: a person who contributes to the fulfillment of a need or
       furtherance of an effort or purpose; "my invaluable
       assistant"; "they hired additional help to finish the work"
       [syn: assistant, helper, help, supporter]
    4: a band (usually elastic) worn around the leg to hold up a
       stocking (or around the arm to hold up a sleeve) [syn:
       garter, supporter]
    5: a support for the genitals worn by men engaging in strenuous
       exercise [syn: athletic supporter, supporter,
       suspensor, jockstrap, jock]