What is Macmillan?
1.
The act of shoving your testicles into the anus of a girl you are having vaginal intercourse with in the missionary position.
May also include shoving your testicles into the vagina while having anal sex.
Akin to an "Armstrong".
"Dude, I was doing this chick and I totally MacMillan'd her. Right in the backseat of my Miata!"
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1.
a term that originated with people that ride horses, since you are supposed to brush them and groom them after a workout; now used to r..