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When your banging your girl and she reaches around to your ass, shoves her finger up your ass and milks your prostate at the same time. Produces intense orgasms and heavy loads.

May also be performed by a third party is one is involved like your girl’s girlfriend, your perverted uncle that likes to watch or your roommate lending a helping hand.
I was slinging ropes last night when I busted. She was giving me a courtesy milk.

Your mom is so kind braaaaahhhh. I can always count on a courtesy milk.

My uncle paid me $50 to watch me and my girl do the nasty. But he gave me a courtesy milk and now I’m kinda creeped.

My roommate walked in on me and Sheila going at it like rabbits. But I had him stay and give me a courtesy milk.
via giphy
by Eaton Holgoode April 20, 2018
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