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.

plural of osmium

(chemistry) An oxide of the metal osmium, OsO₄; it is very poisonous, has a pungent smell and can cause blindness; it is a powerful oxidizing agent, and is used to stain biological materials.

hassium.