1) Having three fold symmetry 2) Symmetric 3) Symmetrical 4) Trigonal 1) Symmetric 2) Symmetrical 3) Trigonal 
• (a.) 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.
1. <geometry> 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. ... 2. <chemical> Rhombohedral iron ore, a division of the hexagonal system embracing the rhombohedron, scalenohedron, etc. ... (23 Aug 199...
Rhom`bo·he'dral adjective (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.) 
[adj] - (crystallography) having three-fold symmetry
trigonal adjective having threefold symmetry