For human anatomy, see Islets of Langerhans An islet is a small island. Definition of Types Rock A "rock", sometimes a synonym for a type of "islet", is a landform composed of rock, lying offshore, having no or minimal vegetation, and uninhabited (see Mōkōlua Rock at right). Sandbar An exposed sandbar is another type of islet. A more technical application is to small land features, isolated by water, lying off the shore of a larger island. And in related fashion, any emergent la… (More on Islets)