When it comes to finding synonyms for the term "sister-in-law," there are plenty of options available. Some commonly used ones include sister by marriage, brother's wife, spouse's sister, in-law relationship, sibling's partner, and family relation. In addition to these, there are also phrases like the wife of one's sibling's spouse, the sister of one's spouse, or the sibling-in-law. While there are different ways to refer to this person in your life, the term "sister-in-law" is the most widely used and recognized. With these synonyms, people can find alternative ways to refer to their sister-in-law without being repetitive or using the same term over and over again.