Breadcrumb Home > Thesaurus > N Cite Synonyms of neptunium Find synonyms for: Noun1. neptunium, Np, atomic number 93, metallic element, metalusage: a radioactive transuranic metallic element; found in trace amounts in uranium ores; a by-product of the production of plutoniumWordNet 3.0 Copyright © 2006 by Princeton University. All rights reserved.Definition and meaning of neptunium (Dictionary) TrendingHere are the facts and trivia that people are buzzing about. January 2021 Current Events: US News The Holocaust (1933–1945) Chinese New Year History, Meaning, and Celebrations Noble Titles and Ranks in a Monarchy The 5 Best Air Purifiers of 2020 Inaugural Trivia Related Content Daily Word Quiz: jerrybuilt Analogy of the Day: Today’s Analogy Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language