What is another word for "trigonal"?

Roget's Thesaurus (1911) lists these synonyms for "trigonal": cube, divide, fold, into, part, place, tern, ternary, the, third, thirdly, three, threefold, thrice, treble, trebleness, trebly, triangular, trichotomous, trichotomy, tricuspid, tridentate, tridentiferous, trifid, trifoliate, trifurcate, trigrammatic, trigrammic, trinal, trine, tripartite, tripartition, tripetalous, triple, triplicate, triplication, triplicity, triquetral, triquetrous, trisect.