The Collaborative International Dictionary of English v.0.48:

Caste \Caste\, n. [Pg. casta race, lineage, fr. L. castus pure,
   chaste: cf. F. caste, of same origin.]
   1. One of the hereditary classes into which the Hindu are
      divided according to the laws of Brahmanism.
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   Note: The members of the same caste are theoretically of
         equal rank, and same profession or occupation, and may
         not eat or intermarry with those not of their own
         caste. The original are four, viz., the Brahmans, or
         sacerdotal order; the Kshatriyas, or soldiers and
         rulers; the Vaisyas, or husbandmen and merchants; and
         the Sudras, or laborers and mechanics. Men of no caste
         are Pariahs, outcasts. Numerous mixed classes, or
         castes, have sprung up in the progress of time.
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   2. A separate and fixed order or class of persons in society
      who chiefly hold intercourse among themselves.
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            The tinkers then formed an hereditary caste.
                                                  --Macaulay.
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   To lose caste, to be degraded from the caste to which one
      has belonged; to lose social position or consideration.
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