Definition of "sister-in-law" [sis•ter-in-law]

• The sister of one's spouse. (noun)
• The wife of one's brother. (noun)
• The wife of the brother of one's spouse. (noun)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "In the morning, I called my sister-in-law and told her to come back over."
• "I called my sister-in-law, who is an elementary school teacher, and told her what was going on."
• "Kevin yanks his cell phone from his pocket and calls his sister-in-law in Queens, the wife of his brother Joe."