/ ləˈguːn; NAmE / noun
1.
a lake of salt water that is separated from the sea by a reef or an area of rock or sand
2.
( NAmE ) a small area of fresh water near a lake or river
3.
( technical ) an artificial area built to hold waste water before it is treated at a sewage works
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WORD ORIGIN
early 17th cent.: from Italian and Spanish laguna , from Latin lacuna pool , from lacus lake.