osmium

noun

Etymology: From Ancient Greek ὀσμή (osmḗ, “smell”) (because of the strong smell of its oxide) + -ium.

1. A chemical element (symbol Os) with atomic number 76: a hard, brittle, heavy, bluish-white transition metal found as a trace element in alloys, mostly in platinum ores.

   “Their latest catalyst includes some osmium.”

2. A single atom of this element.

   “This reaction substitutes a ruthenium for an osmium.”