The Collaborative International Dictionary of English v.0.48:

Appendage \Ap*pend"age\, n.
   1. Something appended to, or accompanying, a principal or
      greater thing, though not necessary to it, as a portico to
      a house.
      [1913 Webster]

            Modesty is the appendage of sobriety. --Jer. Taylor.
      [1913 Webster]

   2. (Biol.) A subordinate or subsidiary part or organ; an
      external organ or limb, esp. of the articulates.
      [1913 Webster]

            Antenn[ae] and other appendages used for feeling.
                                                  --Carpenter.
      [1913 Webster]

   Syn: Addition; adjunct; concomitant.
        [1913 Webster]

WordNet (r) 3.0 (2006):

appendage
    n 1: an external body part that projects from the body; "it is
         important to keep the extremities warm" [syn: extremity,
         appendage, member]
    2: a natural prolongation or projection from a part of an
       organism either animal or plant; "a bony process" [syn:
       process, outgrowth, appendage]
    3: a part that is joined to something larger

Moby Thesaurus II by Grady Ward, 1.0:

135 Moby Thesaurus words for "appendage":
   accession, accessories, accessory, accident, accidental,
   accompaniment, addenda, addendum, additament, addition, additive,
   additory, additum, adherent, adjunct, adjuvant, annex, annexation,
   appanage, appanages, appendages, appendant, appendix, appointments,
   appurtenance, appurtenances, appurtenant, arm, attachment,
   attendant, augment, augmentation, auxiliary, belongings, bough,
   branch, buff, cavaliere servente, choses, choses in action,
   choses in possession, choses local, choses transitory, coda,
   collateral, complement, concomitant, contingency, contingent,
   continuation, corollary, courtier, dangler, dependent, disciple,
   extension, extra, extrapolation, fan, fixture, flunky, follower,
   following, hand, hanger-on, happenstance, heeler, henchman,
   homme de cour, imp, incidental, increase, increment, inessential,
   joint, leg, limb, link, lobe, lobule, man, material things, member,
   mere chance, movables, nonessential, not-self, offshoot, organ,
   other, paraphernalia, parasite, partisan, pendant, perquisites,
   personal effects, pinion, public, pursuer, pursuivant,
   ramification, reinforcement, retainer, runner, satellite, scion,
   secondary, sectary, servant, shadow, side effect, side issue,
   spray, sprig, spur, stooge, subsidiary, successor, superaddition,
   supplement, supporter, switch, tagtail, tail, tailpiece, tendril,
   things, trainbearer, trappings, twig, undergirding, unessential,
   votary, ward heeler, wing