an area of shallow water separated from the sea by low sandy dunes. Compare laguna.
2.
Also, lagune.any small, pondlike body of water, especially one connected with a larger body of water.
3.
an artificial pool for storage and treatment of polluted or excessively hot sewage, industrial waste, etc.
Origin: 1605–15; earlier laguna (singular), lagune (plural) < Italian < Latin lacūna (singular), lacūnae (plural) ditch, pool, akin to lacus basin, lake1; see lacuna
1612, from Fr. lagune, from It. laguna "pond, lake," from L. lacuna "pond, hole," from lacus "pond" (see lake). Originally in ref. to the region of Venice; applied 1769 to the lake-like stretch of water enclosed in a South Seas atoll.