a brittle hard silvery-white element that is a ferromagnetic metal: occurs principally in cobaltite and smaltite and is widely used in alloys. The radioisotope cobalt-60, with a half-life of 5.3 years, is used in radiotherapy and as a tracer. Symbol: Co; atomic no: 27; atomic wt: 58.93320; valency: 2 or 3; relative density: 8.9; melting pt: 1495°C; boiling pt: 2928°C
WordReference Random House Learner's Dictionary of American English © 2026
co•balt /ˈkoʊbɔlt/USA pronunciation
n. [uncountable]
WordReference Random House Unabridged Dictionary of American English © 2026- Chemistry, Nutritiona hard whitish metal element used to produce a blue coloring.
co•balt
(kō′bôlt),USA pronunciation n.
- Chemistry, Nutritiona silver-white metallic element with a faint pinkish tinge, occurring in compounds whose silicates afford important blue coloring substances for ceramics. Symbol: Co;
at. wt.: 58.933;
at. no.: 27;
sp. gr.: 8.9 at 20°C.
- German Kobalt, variant of Kobold kobold
- 1675–85
Collins Concise English Dictionary © HarperCollins Publishers::
'cobalt' also found in these entries (note: many are not synonyms or translations):
Brandt
- CO
- Co
- Likasi
- Ndola
- Thenard's blue
- Thénard's blue
- Venetian blue
- Vitallium
- Waterford glass
- alloy steel
- alnico
- aureolin
- beryllium copper
- blue tit
- blue-tongued lizard
- bomb
- cerulean blue
- cobalt 60
- cobalt bloom
- cobalt blue
- cobalt bomb
- cobalt green
- cobalt violet deep
- cobalt violet light
- cobalt yellow
- cobaltammine
- cobaltic
- cobaltite
- cobaltous
- cobaltous hydroxide
- cohenite
- cyanocobalamin
- danaite
- erythrite
- ferrite
- glaucodot
- goblin
- king's blue
- kobold
- nickel
- oxo process
- pharmacolite
- potassium cobaltinitrite
- skutterudite
- smalt
- smaltite
- superalloy
- tervalent
- zaffer