Mother-in-law (noun)

1. The mother of one's spouse.
2. A woman who is the mother of one's spouse.

Origin:

Late middle english: from mother + in-law.

Examples:

1. She had a difficult relationship with her mother-in-law.
2. He respected his mother-in-law and treated her kindly.
3. She was close to her mother-in-law and considered her a second mother.
4. The mother-in-law lived with them after her husband passed away.
5. The mother-in-law was happy to have a new addition to the family.