mixed marriage

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun Marriage between persons of different races or religions.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun Marriage between people of different socially-distinguished groups, such as different races, cultures or religions.
• noun poker slang A king and a queen of different suits as a starting hand in Texas hold 'em (see marriage (poker slang)).

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun marriage of two people from different races or different religions or different cultures