/ Dictionary / Index T trigonal: Meaning and Definition of Find definitions for: trig•o•nal Pronunciation: (trig'u-nl), [key] — adj. of, pertaining to, or shaped like a triangle; having three angles; triangular. having threefold symmetry. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: trigonal (Thesaurus) trigon trigonal trisoctahedron Related Content Daily Word Quiz: fresco Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language