/ Dictionary / Index R rill: Meaning and Definition of Find definitions for: rill Pronunciation: (ril), [key] a small rivulet or brook. rill Pronunciation: (ril), [key] any of certain long, narrow, straight or sinuous trenches or valleys observed on the surface of the moon. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: rill (Thesaurus) Rilke rillet Related Content Daily Word Quiz: vertigo Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language