The Collaborative International Dictionary of English v.0.48:

Endogamous \En*dog"a*mous\, a. [Endo- + Gr. ? marriage.]
   Marrying within the same tribe; -- opposed to exogamous.
   [1913 Webster]

WordNet (r) 3.0 (2006):

endogamous
    adj 1: characterized by or fit for fertilization by pollen from
           another flower of the same kind [syn: endogamous,
           endogamic] [ant: autogamic, autogamous, exogamic,
           exogamous]
    2: pertaining to or characterized by the custom of marrying only
       within the limits of a clan or tribe [syn: endogamous,
       endogamic] [ant: exogamic, exogamous]