Some one of simple nature that does not have the basic instincts to navigate themselves through life.
Bromandudeguy1: Why is Simple Jack eating toothpaste?
Bromandudeguy2: Because Simple Jack is a real poptart.
When a someone uses their penis to have intercourse with another persons armpit, then follows said action by ejaculating on their chest.
*Phil Collins music playing* Chuck after vigorous hours of pummeling Mikes armpits with his dong, decided to finish off the Double Pits To Chesty and dropped a super mediocre load right on his chest pubes.