ˈsistə(r)ə̇nˌlȯ, -trə̇n-, -tə(r)n- noun
( plural sisters-in-law -tə(r)zə̇n-)
Etymology: Middle English suster-in-lawe; probably from the fact that the canon law forbids marriage with one's spouse's sister or brother
1. : the sister of one's spouse
2.
a. : the wife of one's brother
b. : the wife of one's spouse's brother