To fuck one's brother-in law or sister-in-law.
Ed: "Wait, Jack fucked his wife Jill's sister?"
Eddie: "Yeah he just committed incest-in-law."
by The Elias June 2, 2016
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To fuck one's brother-in law or sister-in-law.
Ed: "Wait, Jack fucked his wife Jill's sister?"
Eddie: "Yeah he just committed incest-in-law."
by The Elias June 2, 2016
Get the Incest-in-law mug.