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1.
The parents of your live-in boyfriend/girlfriend.
I am having my sinlaws over for dinner...I hope I make a good impression since I have been shacking up with their son for a few weeks now and they are not down with the fact we are living in sin.
by PunTiff August 01, 2008

Words related to sinlaws

boyfriend girlfriend inlaws parents shacking up
 
2.
The parent of a partner in a romantic and cohabitating but unmarried relationship.
Sadly, John's sin-laws dropped by the house for Jane's birthday.
by Jim Dempsey August 28, 2004