In polygamy, a wife of one's father who is not one's mother; that is, co-wife of one's mother.
In polygamy, the relationship between one co-wife and another, in respect to their children.
In a lesbian couple, the nonbirth mother (partner of the birth mother) of a child, especially one who takes an equal role in mothering the child.
Another wife of one's husband. Typically used in cases of divorce and subsequent remarriage for one's husband's ex-wife, but sometimes used in polygamy for a co-wife.
A wife who provides domestic or social support, but not love or affection
A wife in law only, such as one who has abandoned her husband