Source : Webster's Revised Unabridged Dictionary (1913)

Endogamy \En*dog"a*my\, n.
   Marriage only within the tribe; a custom restricting a man in
   his choice of a wife to the tribe to which he belongs; --
   opposed to exogamy.

Source : WordNet®

endogamy
     n : marriage within one's own tribe or group as required by
         custom or law [syn: {intermarriage}, {inmarriage}] [ant:
         {exogamy}]