/ Dictionary / Index U ultranet: Meaning and Definition of Find definitions for: ul•tra•net Pronunciation: (ul'tru-net"), [key] — n. Math. a net in a topological space that is residually in every set or its complement in the space. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. ultranationalist ultrapure Related Content Daily Word Quiz: rustic Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language