sister-in-law

Meanings

1. 1
   noun

   A female relative of one's generation, separated by one degree of marriage:

   Though they are not twins, my sister-in-law resembles my wife in almost every way.

2. 2
   noun

   the sister of your spouse

3. 3
   noun

   Co-sister-in-law: The wife of one's sibling-in-law.

Etymology

Inherited from Middle English suster-in-lawe; equivalent to sister + -in-law.