noun, plural sis·ters-in-law.

the sister of one's husband or wife.
the wife of one's brother.
the wife of the brother of one's husband or wife.

Origin of sister-in-law

1400–50; late Middle English. See sister, in, law1 Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for sister-in-law

Contemporary Examples of sister-in-law

Historical Examples of sister-in-law

  • "Well, I'm not going to beat about the bush," continued her sister-in-law abruptly.


    Mr. and Mrs. Haldeman-Julius

  • I found my host at dinner with his wife, little daughter, and sister-in-law.

    In the Heart of Vosges

    Matilda Betham-Edwards

  • His sister-in-law treated him badly and never gave him enough to eat.

  • His sister-in-law wished to see his art, so she poured the rice into the pot.

  • If this young lady is my sister-in-law, surely she and I can settle up our own affairs.

    The Avenger

    E. Phillips Oppenheim

British Dictionary definitions for sister-in-law


noun plural sisters-in-law

the sister of one's husband or wife
the wife of one's brother
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for sister-in-law

mid-15c.; see sister + in-law.

Online Etymology Dictionary, © 2010 Douglas Harper