Definition of "co-sister-in-law" []

• One's husband's brother's wife; or more generally one's spouse's sister-in-law, the sister of one spouse in relation to the siblings of the other spouse. (noun)
• One's brother-in-law or sister-in-law's sister; that is, one's sibling's spouse's sister (one's sister's husband's sister or one's brother's wife's sister). (noun)

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