/ Dictionary / Index H horsehair worm: Meaning and Definition of Find definitions for: horse'hair worm" Pronunciation: [key] any long, slender worm of the phylum Nematomorpha, developing parasitically on insects and crustaceans, and free-living as adults in streams and ponds. Also called Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. horsehair fungus horsehead Related Content Daily Word Quiz: philtrum Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language