Source : Webster's Revised Unabridged Dictionary (1913)

Sphenoid \Sphe"noid\, n.
   1. (Crystallog.) A wedge-shaped crystal bounded by four equal
      isosceles triangles. It is the hemihedral form of a square
      pyramid.

   2. (Anat.) The sphenoid bone.

Sphenoid \Sphe"noid\, a. [Gr. ???; sfh`n a wedge + e'i^dos form:
   cf. F. sph['e]no["i]de.]
   1. Wedge-shaped; as, a sphenoid crystal.

   2. (Anat.) Of or pertaining to the sphenoid bone.

   {Sphenoid bone} (Anat.), an irregularly shaped bone in front
      of the occipital in the base of the skull of the higher
      vertebrates. It is composed of several fetal bones which
      become united the adult. See {Alisphenoid},
      {Basisphenoid}, {Orbitosphenoid}, {Presphenoid}.

Source : WordNet®

sphenoid
     n : butterfly-shaped bone at the base of the skull [syn: {sphenoid
         bone}, {os sphenoidale}]