Synonyms for Gd (same or very similar meaning)
WordNet sense 1 (a nerve agent easily absorbed into the body; a lethal cholinesterase inhibitor that is highly toxic when inhaled):
somanWordNet sense 2 (a ductile silvery-white ductile ferromagnetic trivalent metallic element of the rare earth group):
gadoliniumFrom the ODE community, based on WordNetadd/edit