It's where when you hug someone you rub your hands up and down there back, subtly pulling them closer so your fronts are rubbing against each other. May or may not include grabbing their butt and pressing their crotch against yours.
"He didn't hug her, he porn hugged her."

or

Jaci: *porn hugs for everyone*
by Jaci or Lacy September 3, 2011
Get the porn Hug mug.