The Collaborative International Dictionary of English v.0.48:

Peduncle \Pe*dun"cle\, n. [Formed fr. (assumed) L. pedunculus,
   dim. of pes, pedis, a foot: cf. F. p['e]doncule.]
   1. (Bot.) The stem or stalk that supports the flower or fruit
      of a plant, or a cluster of flowers or fruits.
      [1913 Webster]

   Note: The ultimate divisions or branches of a peduncle are
         called pedicels. In the case of a solitary flower, the
         stalk would be called a peduncle if the flower is
         large, and a pedicel if it is small or delicate.
         [1913 Webster]

   2. (Zool.) A sort of stem by which certain shells and
      barnacles are attached to other objects. See Illust. of
      Barnacle.
      [1913 Webster]

   3. (Anat.) A band of nervous or fibrous matter connecting
      different parts of the brain; as, the peduncles of the
      cerebellum; the peduncles of the pineal gland.
      [1913 Webster]

WordNet (r) 3.0 (2006):

peduncle
    n 1: the thin process of tissue that attaches a polyp to the
         body
    2: stalk bearing an inflorescence or solitary flower
    3: a bundle of myelinated neurons joining different parts of the
       brain [syn: peduncle, cerebral peduncle]