/ Dictionary / Index U ubiquitin: Meaning and Definition of Find definitions for: u•biq•ui•tin Pronunciation: (y-bik'wi-tin), [key] a small protein, present in all eukaryotic cells, that participates in the destruction of defective proteins and in the synthesis of new proteins. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. Ubiquitarian ubiquitous 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