A female caregiver of a child who assumed the parental role through marriage to one of the child's original (usually biological) parents. Most commonly, a step-mother is the second wife of a child's biological father. I live with my mom during the week and then visit my dad and step-mother every other weekend.
Step-mother
STEP-MOTHER. In Latin noverca, is the wife of one's father, who is not the mother of the person spoken of.