When a person does things that you would expect people to do while on an island. The form of any islander activities or gatherings.
Eating pineapple, doing dances in grass skirts, wearing coconuts as a bra, surfing, carving tiki men out of wood, would all be considered islandy things to do.
Krystal: "Your an islander right Matt?"
Krystal: "So do you do islandy things?"