After a prolonged bout of anal sex, the giving party turns the recieving party around and proceeds to thwack them on the forehead with their penis/dildo leaving a brown mushroom in its stead. Also known as the brown mushroom to go, because one does not want to stick around after giving a brown mushroom.
notes: brown mushroom is only theoretical, poo does not actually stick to the penis in quantities that would make this act possible.
Johnny gave Jenny a brown go.
by October 6, 2004
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When you fuck a girl in the ass then slap her in the face with your cock.
I was fucknig your mom in the ass then pulled out for a second and gave her a Brown mushroom tattoo then kept on fucking.
by chaigh September 7, 2008
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