A sex act involving a guy ejaculating on a girl's body without her noticing, then licking it off and pretending it never happened.
It is said that the origin of the word comes from the the french expression : "oiseaux mangeur", which means eating like a goose. Goose, in when eating together, tend to eat very fast as if they hide the food in their throats.
Hey! Did you pull out the Goose-man on me?