/ Dictionary / Index A americium: Meaning and Definition of Find definitions for: am•er•i•ci•um Pronunciation: (am"u-rish'ē-um), [key] — n. Chem. a transuranic element, one of the products of high-energy helium bombardment of uranium and plutonium. Symbol: Am; at. no.: 95. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: americium (Thesaurus) America's Cup Americus Related Content Daily Word Quiz: fervor Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language