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