/ Dictionary / Index R ribbon worm: Meaning and Definition of Find definitions for: rib'bon worm" Pronunciation: [key] any of various slender, unsegmented marine worms of the phylum Nemertea, being able to contract and stretch to an extreme extent. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. ribbon window ribby Related Content Daily Word Quiz: simian Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language