Real Dictionary

osmium in American English
a very hard, bluish-white, amorphous, metallic chemical element, one of the platinum metals: it occurs in the form of an alloy with platinum and iridium and is used in pen points, electric light filaments, etc., and as a catalyst: symbol, Os; at. no., 76
noun: 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; at. wt.: 190.2; at. no.: 76; s

osmium in British English
noun: 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; a