/ Dictionary / Index U ultrathin: Meaning and Definition of Find definitions for: ul•tra•thin Pronunciation: (ul"tru-thin'), [key] — adj. extremely thin: an ultrathin wristwatch. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. Ultrasuede ultratropical 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