/ Dictionary / Index A arroyo: Meaning and Definition of Find definitions for: ar•roy•o Pronunciation: (u-roi'ō), [key] — pl. -os. (chiefly in southwest U.S.) a small steep-sided watercourse or gulch with a nearly flat floor: usually dry except after heavy rains. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: arroyo (Thesaurus) arrowy Arroyo Grande Related Content Daily Word Quiz: denizen Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language