Sister-in-law is a woman who marries your brother or is your husband's sister.
(noun)An example of sister in law is the sister of your brother.
See sister-in-law in Webster's New World College Dictionary
noun pl. sisters-in-law
See sister-in-law in American Heritage Dictionary 4
noun pl. sis·ters-in-law (sĭsˈtərz-)
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