(Verb) A sexual act that occurs when a man gets on all fours with his partners head between his knees. His partner proceeds to give him a blowjob and when he orgasms he squeals like a pig as his partner swallows his ejaculate.
She said she wanted me to be an animal in bed, so we did the hog-swallow.
The most literal sense of the expression "hog heaven" is a filthy pig sty with plenty of fresh slop on which to feed. Thus the pigs would be just about as happy as they could be.
People extend this idea to other, perhaps less filthy, situations. I've often heard people say someone was in hog heaven for just about any serendipitous occurrence.
So he walks in and finds a bathtub full of whiskey. Man, he was in hogheaven!
The act of sticking one's face between a stud's glutes--tossing and blowing your heart out--thus allowing the glutes to oscillate on your face.
Marcus: So what was the high point of your date?
Kelley: At the end of the night, Pedro was hog troughing me until I thought I would be split in two. Serious fun, could not stop laughing.
Marcus: What did you do last night?
Kelley: Bible, I spent all night hog troughing gym crush, making him moan like a pregnant cow giving birth.