A tombolo is a geological landform characterized as a sandy or shingle isthmus. It is formed by deposition processes that result in an island becoming attached to the mainland via a narrow strip of land, such as a spit or bar. Once this connection is established, the island is referred to as a tied island.
The term originates from the Italian word "tombolo," which translates to "pillow" or "cushion." While it is sometimes incorrectly translated as an ayre, the term specifically describes these coastal deposition features.