The Collaborative International Dictionary of English v.0.48:

geniohyoid \ge`ni*o*hy"oid\ (j[=e]`n[i^]*[-o]*h[imac]"oid), a.
   [Gr. ge`neion the chin + E. hyoid.] (Anat.)
   Of or pertaining to the chin and hyoid bone; as, the
   geniohyoid muscle.
   [1913 Webster] Genip