Definition of cobalt in US English:



  • 1The chemical element of atomic number 27, a hard silvery-white magnetic metal.

    Cobalt is chiefly obtained as a byproduct from nickel and copper ores. It is a transition metal similar in many respects to nickel. Its main use is as a component of magnetic alloys and those designed for use at high temperatures

    • ‘This packing arrangement is also observed for many metals, including rubidium, osmium, cobalt, zinc, and cadmium.’
    • ‘They blended and heated plutonium with gallium and cobalt and then slowly cooled the molten mixture.’
    • ‘Besides gold and diamonds, the area is rich in copper, uranium, palladium and cobalt, as well as coltan ore.’
    • ‘We are already exporting gold and we have substantial resources of silver, uranium, nickel and cobalt, the deposits of which need further investigation.’
    • ‘The slow growth rate is thought to enhance the absorption of heavy metals like copper and cobalt from sea water.’
    1. 1.1
      as modifier ‘a cobalt sky’
      short for cobalt blue
      • ‘His stormy cobalt eyes glanced down at her and he sighed again.’
      • ‘He took her hand and kissed it, his cobalt eyes twinkling.’
      • ‘What snatches of blue sky she could see were deepening from azure to cobalt and she thought she saw the first star twinkling already.’
      • ‘I got out my sketch book and showed him some of the paintings I'd done of lizard head spires piercing skies of cobalt and turpentine.’
      • ‘His gaze caught mine and for a second his cobalt eyes were a mirror for the sun.’
      • ‘Other houses' bathrooms are characterised by bright cobalt blues or pearl whites.’
      • ‘The purple on his surcoat made his striking cobalt eyes seem deep violet.’
      • ‘Not only were his eyes lacking their normal cobalt hue and his pupils disturbingly restricted but now his eyes were blood shot as well.’
      • ‘On a walk through the five-acre garden you encounter great bushes of Blue Bonnet, whose huge flower heads vary from powder blue to cobalt.’
      • ‘He lifted up his cobalt eyes to his friend for only a split second and then glanced back down.’
      • ‘The softly tailored look is also very much in this season with glowing colours such as cobalt and rich greens coupled with subtly shaded creams and browns.’
      • ‘It was of dark cobalt, running to purple, and had golden thread work all along the hem and sleeves.’
      • ‘Side plates at each place setting are coloured a brilliant turquoise or patterned in cobalt or shaped like river boats.’
      • ‘He muttered something in angry fluent French, as he tilted his head back and looked up at the star-dusted cobalt sky.’
      • ‘It was February with cobalt skies, snappy air, and a fresh blanket of snow.’
      • ‘Above, the serrated edge of the granite ridge cuts through the cobalt sky.’
      • ‘He left a tip and walked outside to his cobalt truck, driving away only a few moments later.’
      • ‘This past week in the forest park, the fiery foliage set against cobalt skies was a sight to behold.’
      • ‘And then came the third line, a collection in shades of aquamarine, cobalt, ethereal blue, sky blue, and dream blue.’
      • ‘The cloudless sky was the color of cobalt, so blue he felt he could breathe it in and out and become a part of it.’


Late 17th century: from German Kobalt ‘imp, demon’ (because the presence of cobalt-bearing ore made it more difficult to extract silver, and miners believed that it was harmful to the silver ore with which it occurred).