sister in lawglossary / SISTER-IN-LAW sister-in-law. The sister of one’s spouse or the wife of one’s brother. • The wife of one’s spouse’s brother is also sometimes considered a sister-in-law. Pl. sisters-in-law. 词条贡献者 法律翻译玉晶,毕业于英国一流的高级翻译学院,专注翻译各类与通用数据保护条例有关的法律文件。