Home Help Word English Spanish French Russian German Italian Chinese (Trad.) Chinese (Simpl.) Portuguese Arabic Turkish Greek » Definition of " lagoon " in English English Dictionary Results Lagoon A shallow sound, channel, pond, or lake, especially one into which the sea flows; as, the lagoons of Venice. n. Lagoon A lake in a coral island, often occupying a large portion of its area, and usually communicating with the sea. See Atoll. n.