/ Dictionary / Index T tachy-: Meaning and Definition of Find definitions for: tachy- Pronunciation: [key] a combining form meaning “swift,” used in the formation of compound words:Cf. tachygraphy. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. tachometer tachycardia Related Content Daily Word Quiz: profiterole Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language