/ Dictionary / Index H hydrilla: Meaning and Definition of Find definitions for: hy•dril•la Pronunciation: (hī-dril'u), [key] — n. a submerged aquatic plant, Hydrilla verticillata, native to the Old World, that has become a pest weed in U.S. lakes and waterways. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: hydrilla (Thesaurus) hydride hydriodic Related Content Daily Word Quiz: profiterole Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language