/ Dictionary / Index T theta wave: Meaning and Definition of Find definitions for: the'ta wave" Pronunciation: [key] — Physiol. Physiol. any of the brain waves constituting theta rhythm. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. theta rhythm Thetford Mines Related Content Daily Word Quiz: frugal Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language