goise can mean anything you want it to, and it also means nothing. It is a universal word that is best used when directed towards an unsuspecting stranger. Other forms include the noun "goiserclause" and the noun "goiser" both used to describe a person.
when driving down the road you can roll down the window and yell to someone on the sidewalk "GOISE!"
or you can say "that guy is a goiser"
or "hey goiserclause, come here"