marriage or sexual relations between a man and woman of different races, esp., in the U.S., between a white and a black
See miscegenation in American Heritage Dictionary 4
(mĭ-sĕjˌə-nāˈshən, mĭsˌĭ-jə-)
noun
Cohabitation, sexual relations, marriage, or interbreeding involving persons of different races, especially in historical contexts as a transgression of the law.