/ Dictionary / Index U unnilpentium: Meaning and Definition of Find definitions for: un•nil•pen•ti•um Pronunciation: (y"nil-pen'tē-um), [key] — n. provisional name for the transuranic element with atomic number 105. Symbol: Unp&hasp; Also called Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. unnilhexium unnilquadium 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