When it has been so long since you have gotten any action you get a chubby from just hugging or kissing a girl. The situation is usually when you are either saying hello or goodbye. Usually leading to an awkward greeting or an embarrassing walk away at half-mass.
"Dude, it's been so long since I've had sex, I gave Jennifer a kiss good-bye and got the ol' hug n chub. As I walked to my car I had to tuck it in my waistband so no one could see it!"