Giz is an arabic slang used to describe good looking girls, and in some nations (Denmark) boys too.
A giz is a person who you do not have feelings for or any future intentions about. The intensions will end once the night does.
Oh bro, look at that giz ! should I make a move?
Did you giz a little last night?
OMG there's so many giz at EGMUN16!