Sibling-in-law also refers to the reciprocal relationship between a person's spouse and their sibling's spouse. In Indian English this can be referred to as a co-sibling (specificity a co-sister, for the wife of one's sibling-in-law, or co-brother, for the husband of one's sibling-in-law).
the sister of your husband or wife. The brother of your husband or wife is your brother-in-law. sister-in-law. noun. the wife of your.
(uncommon) One's wife's sister's husband; or more generally one's spouse's (in the plural) Men whose brother and sister are married to each other.
One's husband's brother's wife; or more generally one's spouse's sister-in-law, the wife of a brother in relation to the spouses of his siblings. (in the plural) Women.