The Collaborative International Dictionary of English v.0.48:

Spadix \Spa"dix\, n.; pl. L. Spadices, E. Spadixes. [L., a
   palm branch broken off, with its fruit, Gr. ?.]
   1. (Bot.) A fleshy spike of flowers, usually inclosed in a
      leaf called a spathe.
      [1913 Webster]

   2. (Zool.) A special organ of the nautilus, due to a
      modification of the posterior tentacles.
      [1913 Webster]

WordNet (r) 3.0 (2006):

spadix
    n 1: the fleshy axis of a spike often surrounded by a spathe