/ Dictionary / Index C cardioid: Meaning and Definition of Find definitions for: car•di•oid Pronunciation: (kär'dē-oid"), [key] — n. Math. a somewhat heart-shaped curve, being the path of a point on a circle that rolls externally, without slipping, on another equal circle. Equation:(1−cosA). r = a Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: cardioid (Thesaurus) cardiograph cardiolipin Related Content Daily Word Quiz: cautious Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language