Gelnn Theodore Seaborg gelnnt·heo·do·reseaborg uncommon noun 1. United States chemist who was one of the discoverers of plutonium (1912-1999) SynonymsSeaborgGlenn T. SeaborgGelnn Theodore Seaborg Related words Broader terms chemist WordNet 2.1 (Princeton University). WordNet 2.1 Copyright Princeton University. All rights reserved.