The Collaborative International Dictionary of English v.0.48:

Intermarry \In`ter*mar"ry\, v. i.
   To become connected by marriage between their members; to
   give and take mutually in marriage; -- said of families,
   ranks, races, castes, etc.
   [1913 Webster]

         About the middle of the fourth century from the
         building of Rome, it was declared lawful for nobles and
         plebeians to intermarry.                 --Swift.
   [1913 Webster]

WordNet (r) 3.0 (2006):

intermarry
    v 1: marry within the same ethnic, social, or family group