/ Dictionary / Index H heartworm: Meaning and Definition of Find definitions for: heart•worm Pronunciation: (härt'wûrm"), [key] — n. a parasitic nematode, Dirofilaria immitis, transmitted by mosquito and invading the heart and pulmonary arteries of dogs, wolves, and foxes throughout its range in tropical, subtropical and, more recently, temperate regions around the world. the disease caused by infection with heartworm. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. heartwood hearty Related Content Daily Word Quiz: paradox Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language