Man-o-plasm refers to a '
load' of very viscous, cloudy
white semen that is ejaculated from a man's
wanger upon orgasm. It is named 'man-o-plasm' as it resembles the eerie substance that ghostly apparitions are said to leave behind (made famous in the movie Ghostbusters).
See also: rectoplasm
Egon: there were definitely ghosts here
Peter, look, there's some ectoplasm in the corner...
Peter: Egon, you fuck, that isn't ectoplasm.. Ray was over in that corner there earlier with a copy of Hustler.
Egon:
shit, then it's just a load of man-o-plasm. Goddamn Ray, you filthy cunt.
Ray: Aw christ, WHAT NOW?!?