The Collaborative International Dictionary of English v.0.48:

Hypohyal \Hy`po*hy"al\, a. [Pref. hypo- + Greek letter ?.]
   (Anat.)
   Pertaining to one or more small elements in the hyoidean arch
   of fishes, between the caratohyal and urohyal. -- n. One of
   the hypohyal bones or cartilages.
   [1913 Webster]