A more thorough explanation:

Definition: The head woman of a family, either married or single.

Examples:

• Lucy was the materfamilias of her household, making all the important decisions for her family.
• Even though she was unmarried, Sarah was considered a materfamilias because she took care of her younger siblings and managed the household.

The examples show that a materfamilias is a woman who is in charge of a family, whether she is married or not. She is responsible for making important decisions and managing the household.