/ Dictionary / Index T thermal unit: Meaning and Definition of Find definitions for: ther'mal u"nit Pronunciation: [key] a unit of heat energy or of the equivalent of heat energy in work. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. thermal underwear thermanesthesia Related Content Daily Word Quiz: wizened Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language