/ Dictionary / Index U unnilseptium: Meaning and Definition of Find definitions for: un•nil•sep•ti•um Pronunciation: (y"nil-sep'tē-um), [key] — n. provisional name for the transuranic element with atomic number 107. Symbol: Uns&hasp; Also called Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. unnilquadium unnumbered 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