/ Dictionary / Index T tridymite: Meaning and Definition of Find definitions for: trid•y•mite Pronunciation: (trid'u-mīt"), [key] — n. Mineral. a polymorph of quartz occurring in the form of small crystals, commonly twinned, in siliceous volcanic rocks. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: tridymite (Thesaurus) triduum triecious Related Content Daily Word Quiz: dissonant Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language