/ Dictionary / Index H hypothallus: Meaning and Definition of Find definitions for: hy•po•thal•lus Pronunciation: (hī"pu-thal'us, hip"u-), [key] — pl. -thal•li a layer of hyphae rimming the thallus of certain lichens. a filmlike residue at the base of the sporangia of certain slime molds. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. hypothalamus hypothec Related Content Daily Word Quiz: supercilious Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language