cobalt

noun

co·​balt ˈkō-ˌbȯlt 

1

: a magnetic metallic element that is used especially in alloys, in batteries, and as a pigment in paint and glass see Chemical Elements Table

2

: cobalt blue sense 2

Did you know?

The metallic element "cobalt" ultimately draws its name from folklore. In Middle High German, "kobolt" denoted a usually helpful household elf that engaged in nasty pranks only when it was offended. Later, early Modern German Kobold came to refer to a variety of less helpful goblins inhabiting fields and mountains. The variant "Kobolt" in the 16th century was applied by German miners to ores containing the metal cobalt, which they considered to be worthless; they believed that mountain goblins had spoiled adjacent silver ores, or had stolen the silver within the ore. The metal itself in relatively pure form was not produced and described until the 17th century, when "cobalt," with its first letter influenced by New Latin cobaltum, became part of the international language of science.

Examples of cobalt in a Sentence

Recent Examples on the Web

Spotted arriving in Sydney wearing a cobalt-blue paisley headscarf tied over her new crop, narrow Chanel sunglasses, and an all-black ensemble, Robbie was ready to embrace the fast-approaching Australian summer. — Anna Cafolla, Vogue, 5 Nov. 2026

Beijing treats 70% import dependence as an implicit red line – which puts copper, lithium, cobalt, nickel, bauxite and iron ore under a hard national security constraint to expand supply abroad, Wang said. — Anniek Bao, CNBC, 4 Nov. 2026

To forge the target in the first place, Rice University scientists bound small diamond grains with cubic boron nitride and cobalt using spark plasma sintering. — Mrigakshi Dixit, Interesting Engineering, 4 Nov. 2026

Meanwhile, in 2016 and 2020, the only major American mining company active in Congo sold its stakes in two substantial copper-cobalt deposits, its only remaining stakes in the country, to a Chinese mining company. — Tom Moerenhout, Foreign Affairs, 4 Nov. 2026

Word History

Etymology

German Kobalt, alteration of Kobold, literally, goblin, from Middle High German kobolt; from its occurrence in silver ore, believed to be due to goblins

First Known Use

circa 1872, in the meaning defined at sense 1

Phrases Containing cobalt

• cobalt blue
• cobalt chloride

Rhymes for cobalt

• asphalt
• assault
• basalt
• default
• exalt
• gestalt
• alt
• fault
• gault
• halt
• malt
• sault

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Kids Definition

cobalt

noun

co·​balt ˈkō-ˌbȯlt 

: a tough shiny silver-white magnetic metallic element that is found with iron and nickel and is used especially in alloys see element

Etymology

from German Kobalt "cobalt," an altered form of Kobold, literally, "goblin"; so called because its appearance in silver ore was thought to have been the work of goblins who left it in place of silver which they stole

Medical Definition

cobalt

noun

co·​balt ˈkō-ˌbȯlt 

: a tough lustrous silver-white magnetic metallic element that is related to and occurs with iron and nickel and is used especially in alloys

—symbol Co see Chemical Elements Table