/ Dictionary / Index H heptad: Meaning and Definition of Find definitions for: hep•tad Pronunciation: (hep'tad), [key] — n. the number seven. a group of seven. an element, atom, or group having a valence of seven. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: heptad (Thesaurus) heptachord heptagon Related Content Daily Word Quiz: inutiae Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language