/ Dictionary / Index T tachycardia: Meaning and Definition of Find definitions for: tach•y•car•di•a Pronunciation: (tak"i-kär'dē-u), [key] — n. Med. excessively rapid heartbeat. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: tachycardia (Thesaurus) tachy- tachygraph 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