Legal Definitions - mother-in-law

MOTHER-IN-LAW

A mother-in-law is the mother of a person's spouse.

• My husband's mother is my mother-in-law.
• When I got married, I gained a mother-in-law.

These examples illustrate that a mother-in-law is the mother of someone's spouse. In the first example, the speaker is referring to their husband's mother as their mother-in-law. In the second example, the speaker is talking about gaining a mother-in-law when they got married.