/ Dictionary / Index U ultraclean: Meaning and Definition of Find definitions for: ul•tra•clean Pronunciation: (ul"tru-klēn'), [key] — adj. extremely clean, esp. free of germs: an ultraclean laboratory. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. ultracentrifuge ultraconservative Related Content Daily Word Quiz: ontiguous Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language