The Collaborative International Dictionary of English v.0.48:

Ganoid \Ga"noid\, a. [Gr. ? brightness + -oid.] (Zool.)
   Of or pertaining to Ganoidei. -- n. One of the Ganoidei.
   [1913 Webster]

   Ganoid scale (Zool.), one kind of scales of the ganoid
      fishes, composed of an inner layer of bone, and an outer
      layer of shining enamel. They are often so arranged as to
      form a coat of mail.
      [1913 Webster]

WordNet (r) 3.0 (2006):

ganoid
    n 1: primitive fishes having thick bony scales with a shiny
         covering [syn: ganoid, ganoid fish]