sisters-in-law

/S IH1 S T ER0 Z IH0 N L AO0/
noun
  1. 1

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

  2. 2

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

Source: https://en.wiktionary.org/wiki/sister-in-law, https://en.wiktionary.org/wiki/sisters-in-law