/ Dictionary / Index U ultrafast: Meaning and Definition of Find definitions for: ul•tra•fast Pronunciation: (ul"tru-fast', -fäst'), [key] — adj. extremely fast: ultrafast computers. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. ultradian ultrafiche Related Content Daily Word Quiz: feline Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language