/ Dictionary / Index U unsustainable: Meaning and Definition of Find definitions for: un•sus•tain•a•ble Pronunciation: (un"su-stā'nu-bul), [key] — adj. not sustainable; not to be supported, maintained, upheld, or corroborated. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. unsuspected unswathe Related Content Daily Word Quiz: endear Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language