Trigonal

from WordNet (r) 3.0 (2006)

trigonal
    adj 1: having threefold symmetry [syn: {rhombohedral},
           {trigonal}]

from The Collaborative International Dictionary of English v.0.48

Trigonid \Tri"go*nid\
   [Webster 1913 Suppl.] Trigonal \Trig"o*nal\, a.
   Having three angles, or corners; triangular; as, a trigonal
   stem, one having tree prominent longitudinal angles.
   [1913 Webster]
   [1913 Webster]