Miscegenation

Miscegenation () is the mixing of different racial groups with marriage, relationship, sexual relations, and procreation.
The word "miscegenation" has been used since the 19th century. It is often the name given to describe interracial marriage, interracial dating and interracial sex. In the past, it has been used to describe the study of human race mixtures. 
Today, the use of the phrase is considered outdated and offensive.