​PENINSULA (Lat. paeninsnla, from paene, almost, and insula, an island), in physical geography, a piece of land nearly surrounded by water. In its original sense it connotes attachment to a larger land-mass by a neck of land (isthmus) narrower than the peninsula itself, but it is often extended to apply to any long promontory, the coast-line of which is markedly longer than the landward boundary.