[oz-mee-uh m]

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.

Origin of osmium

1795–1805; < New Latin < Greek osm(ḗ) smell + -ium -ium; named from the penetrating odor of one of its oxides
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for osmium

Historical Examples of osmium

  • But the osmium and uranium alloyed with it are something else.

    The Planet Strappers

    Raymond Zinke Gallun

  • The osmium filament appeared in 1905 and its invention is due to Welsbach, who had produced the marvelous gas-mantle.

    Artificial Light

    M. Luckiesh

  • Owing to its extreme brittleness, osmium was finely divided and made into a paste of organic material.

    Artificial Light

    M. Luckiesh

  • The telephone relay consists of a microphone C, Fig. 25, formed of the two pieces of osmium iridium alloy.

  • An alloy of iridium and osmium (artificial or native) has been employed for tipping the nibs of gold pens (everlasting pens).

British Dictionary definitions for osmium



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

Word Origin for osmium

C19: from Greek osmē smell, so called from its penetrating odour
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for osmium

metallic element, 1803, coined in Modern Latin by its discoverer, English chemist Smithson Tennant (1761-1815) from Greek osme "smell, scent, odor" good or bad (cognate with Latin odor; see odor). So called for the strong smell of its oxide.

Online Etymology Dictionary, © 2010 Douglas Harper

osmium in Medicine



n. Symbol Os

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




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.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.