GD uncommon noun 1. a nerve agent easily absorbed into the body; a lethal cholinesterase inhibitor that is highly toxic when inhaled Synonymssoman 2. a ductile silvery-white ductile ferromagnetic trivalent metallic element of the rare earth group Synonymsgadoliniumatomic number 64 Related words Broader terms metallic elementorganophosphate nerve agent Parts gadolinitesamarskite WordNet 2.1 (Princeton University). WordNet 2.1 Copyright Princeton University. All rights reserved.