noun

1. any of the distinct, hereditary Hindu social classes, each traditionally, but no longer officially, excluded from social dealings with the others
2. any exclusive and restrictive social or occupational class or group
3. rigid class distinction based on birth, wealth, etc., operating as a social system or principle
4. any of the differentiated types of individuals in a colony of social insects

Etymology: Fr < Port casta, breed, race, caste < L castus, pure, chaste, orig., cut off, separated, pp. of carere, to be cut off from < IE base *es-, to cut > MIr cess, spear