The Collaborative International Dictionary of English v.0.48:

Hyoid \Hy"oid\, a. [Gr. ? fr. the letter [Upsilon] + e'i^dos
   form: cf. F. hyo["i]de.]
   1. Having the form of an arch, or of the Greek letter upsilon
      [[Upsilon]].
      [1913 Webster]

   2. (Anat.) Of or pertaining to the bony or cartilaginous arch
      which supports the tongue. Sometimes applied to the tongue
      itself.
      [1913 Webster]

   Hyoid arch (Anat.), the arch of cartilaginous or bony
      segments, which connects the base of the tongue with
      either side of the skull.

   Hyoid bone (Anat.), the bone in the base of the tongue, the
      middle part of the hyoid arch.
      [1913 Webster]

WordNet (r) 3.0 (2006):

hyoid bone
    n 1: a U-shaped bone at the base of the tongue that supports the
         tongue muscles [syn: hyoid, hyoid bone, os hyoideum]