[ oz-mee-uhm ]
/ ˈɒz mi əm /
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noun Chemistry.

a hard, heavy, metallic element having the greatest density of the known elements and forming octavalent compounds, as OsO4 and OsF8: used chiefly as a catalyst, in alloys, and in the manufacture of electric-light filaments. Symbol: Os; atomic weight: 190.2; atomic number: 76; specific gravity: 22.57.



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Origin of osmium

1795–1805; <New Latin <Greek osm() smell + -ium-ium; named from the penetrating odor of one of its oxides

British Dictionary definitions for osmium

/ (ˈɒzmɪəm) /


a very hard brittle bluish-white metal occurring with platinum and alloyed with iridium in osmiridium: used to produce platinum alloys, mainly for pen tips and instrument pivots, as a catalyst, and in electric-light filaments. Symbol: Os; atomic no: 76; atomic wt: 190.2; valency: 0 to 8; relative density: 22.57; melting pt: 3033±30°C; boiling pt: 5012±100°C
C19: from Greek osmē smell, so called from its penetrating odour

Medical definitions for osmium

[ ŏzmē-əm ]

n. Symbol Os

A hard metallic element, found in small amounts in osmiridium and platinum ores. Atomic number 76.

Scientific definitions for osmium

[ ŏzmē-əm ]


A hard, brittle, bluish-white metallic element that is the densest naturally occurring element. It is used to make very hard alloys for fountain pen points, electrical contacts, and instrument pivots. Atomic number 76; atomic weight 190.2; melting point 3,000°C; boiling point 5,000°C; specific gravity 22.57; valence 2, 3, 4, 8. See Periodic Table.
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