when two guys penetrate the same girl's pussy.
the girl lies on her back on top of guy #1, who is also lying on his back. standing in front of her is guy #2, who fucks her missionary. the position is very similar to
double penetration, except with guy #1
fucking her pussy instead of her asshole.
the top of guy #1's dick is touching the floor of the girl's pussy, while the top of guy #2's dick is touching the roof of her pussy. the bottom halves of both dicks rub against each other, which can potentially get
uncomfortable without lube.
this can be very pleasurable for the girl, who's essentially taking one dick with ~1.5-2x the girth. a popular variation has the girl lying on her stomach instead, allowing guy #1 to make out with her and/or guy #2 to spank her.