What is Enamel ?
Enamel is (noun) 1. a very hard covering of colour The enamel of the painting had begun to crack. 2. a hard coloured coating fixed to metal by heating 3. the hard coating on the teeth If the enamel of a tooth gets damaged the tooth will soon start to discolour. (verb) to cover with enamel This must have taken a long time to enamel. Synonym coat (NOTE: enamelling enamelled. The US spelling is enameling enameled.)
source: Easier English, Student Dictionary Upper Intermediate Level