sea Definition in the Cambridge English Dictionary
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Definition of “sea” - English Dictionary

Definition of "sea" - American English Dictionary

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seanoun [C/U]

 us   /si/
a ​largearea of ​saltwater that is ​partly or ​completelysurrounded by ​land, or the ​saltwater that ​covers most of the ​surface of the ​earth: [C] the ​Caribbean/Mediterranean Sea [C] The seas are ​filled with ​creatures we ​know nothing about. If you ​travel by sea, you go in a ​ship.
(Definition of sea from the Cambridge Academic Content Dictionary © Cambridge University Press)

Definition of "sea" - British English Dictionary

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seanoun

uk   us   /siː/
A1 [C or U] the ​saltywater that ​covers a ​largepart of the ​surface of the ​earth, or a ​largearea of ​saltywater, ​smaller than an ​ocean, that is ​partly or ​completelysurrounded by ​land: the ​Mediterranean Sea We went ​swimming in the sea. The sea was calm/​smooth/​choppy/​rough when we ​crossed the Channel. The ​refugees were at sea (= in a ​boat on the sea a ​long way from ​land) for 40 ​days before ​reachingland. When we ​moved to the US, we ​sentour things by sea (= in a ​ship). We ​spent a ​week by the sea (= on the ​coast) this ​year. Soon we had ​left the ​marina and were ​heading towards the ​open sea (= the ​part of the sea a ​long way from ​land).a sea of sth a ​largeamount or ​number of something: The ​teacherlooked down and ​saw a sea of ​smilingfaces.put (out) to sea (of a ​ship) to ​leave a ​port and ​start a ​journey: The ​boats will put (out) to sea on this evening's high ​tide. [C] one of the ​large, ​flatareas on the ​moon that in the past were ​thought to be seas
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(Definition of sea from the Cambridge Advanced Learners Dictionary & Thesaurus © Cambridge University Press)
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