concubine

n. mistress, kept woman; secondary wife (in cultures which allow more that one wife)

Concubinage is the state of a woman or youth in an ongoing, quasi-matrimonial relationship with a man of higher social status. Typically, the man has an official wife and, in addition, one or more concubines. Concubines have limited rights of support from the man, and their offspring are publicly acknowledged as the man's children, albeit of lower status than children born by the official wife or wives.
See more at Wikipedia.org...

Noun
1. a woman who cohabits with an important man
(synonym) courtesan, doxy, odalisque, paramour
(hypernym) mistress, kept woman, fancy woman

n. concubine, mistress

n. cohabitant, one who cohabits; concubine, mistress, kept woman

n. concubine, secondary wife, mistress

n. husband de facto, common law husband