/ Dictionary / Index H hypersomnia: Meaning and Definition of Find definitions for: hy•per•som•ni•a Pronunciation: (hī"pur-som'nē-u), [key] — n. Pathol. a tendency to sleep excessively. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: hypersomnia (Thesaurus) hypersexual hypersonic Related Content Daily Word Quiz: simian Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language