osmium Definition
osmiumnoun 1. chem.(symbol Os, atomic number 76) a very hard dense bluish-white metal, the densest known element, used as a catalyst, and as a hardening agent in alloys with platinum and iridium, eg in pen nibs.
Etymology: 19c: from Greek
osme smell (because of the unpleasant pungent smell of one of its forms, osmium tetroxide) + -ium.