Pump Action Cumshot.
Pump Action Cumshot refers to an extremely powerful ejaculation from a man to his girlfriend (or whoever happens to be blowing him), often considered "like a pump action shotgun going off." Normally this kind of ejaculion can be achieved by a male with some very large and productive testicles, and can be best achived by the type of girl who can, (metaphorically in most cases) "Suck a Golf Ball through a garden hose." A large range must be achived when drenching the girl's face with semen in order for that particular blowjob/comshot to be considered a "Pump Action Cumshot."
So, I was suckin' his dick real good when right when I thought he was gonna quit, he just exploded and gave me a total fuckin' P.A.C.S. !!!