When a guy tagging along with his girlfriend, who is shopping at a girly store (usually in a mall), runs into one of his male friends who is also with their girlfriend in the same store. The result being that they can both talk about masculine "guy things" and feel better about themselves being in a girly store.
guau is a way of saying wow in spanish. it’s the equivalent of saying something similar like “wowlation”, and just means that you acknowledged something that had happened when in a conversation