What is "tombolo"

sand-bar joining an island to the mainland, 1899, from Italian tombolo "sand dune," from Latin tumulus "hillock, mound, heap of earth," from PIE root *teue- (2) "to swell" (see thigh).

n. A spit of sand linking an island to the mainland (or to another island), formed by longshore drift.

A tombolo, from the Italian tombolo, derived from the Latin tumulus, meaning 'mound', and sometimes translated as ayre, is a deposition landform in which an island is attached to the mainland by a narrow piece of land such as a spit or bar. Once attached, the island is then known as a tied island. Several islands tied together by bars which rise above the water level are called a tombolo cluster. Two or more tombolos may form an enclosure (called a lagoon) that can eventually fill with sediment. A tombolo may be considered to be a type of isthmus.