/ Dictionary / Index T triac: Meaning and Definition of Find definitions for: tri•ac Pronunciation: (trī'ak), [key] — n. Electronics. a type of thyristor designed for electronic control of the current supplied to a circuit, used esp. in dimmers for lighting systems. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. triable triacetate Related Content Daily Word Quiz: cygnet Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language