Source : Webster's Revised Unabridged Dictionary (1913)

Rhombohedral \Rhom`bo*he"dral\, a. (Geom. & Crystallog.)
   Related to the rhombohedron; presenting the form of a
   rhombohedron, or a form derivable from a rhombohedron;
   relating to a system of forms including the rhombohedron and
   scalenohedron.

   {Rhombohedral iron ore} (Min.) See {Hematite}.

   {Rhombohedral system} (Crystallog.), a division of the
      hexagonal system embracing the rhombohedron,
      scalenohedron, etc.

Source : WordNet®

rhombohedral
     adj : having three-fold symmetry [syn: {trigonal}]