sea

a  : the salt water that covers much of the Earth's surface — often used with the — often used before another noun (literary) — see also high seas

b  [count] or Sea : a large body of water that is part of the sea or that has land around part or all of it — see color picture on this page; see also seven seas

[count] : an area of the sea — used to describe the movement of the water in the sea — often plural

[count] : a large amount or number of people or things spread over a large area — usually singular — sometimes used figuratively

[count] technical or Sea : one of the large, flat areas on the moon or on Mars