snugit

During heterosexual intercourse in the missionary position the female moves her legs btween those of the male, thus making the fit of the vagina on the penis more snug resulting in more pleasure.

Snugit is done during heterosexual intercourse in the missionary position when the femle moves her legs to in between the male's legs to tighten the vagina on the penis.
Ultimate Snugit is when the female next crosses her legs to make the fit on the penis even tighter.