color theory cobalt definition
Full Definition of COBALT. 1. : a tough lustrous silver-white magnetic metallic element that is related to and occurs with iron and nickel and is used especially in alloys â see element table.2. : cobalt blue 2.See cobalt defined for English-language learners.See cobalt defined for kids. a tough lustrous silver-white magnetic metallic element that is related to and occurs with iron and nickel and is used especially in alloys â see element table. 2. : cobalt blue 2. See cobalt defined for English-language learners. See cobalt defined for kids.