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