Definition of sea
1a
: a great body of salt water that covers much of the earth
broadly
: the waters of the earth as distinguished from the land and air
b
: a body of salt water of second rank more or less landlocked
the Mediterranean sea
c
: ocean
d
: an inland body of water
—used especially for names of such bodies the Caspian Sea
2a
: surface motion on a large body of water or its direction
also
: a large swell or wave
—often used in plural heavy seas
b
: the disturbance of the ocean or other body of water due to the wind
3
: something likened to the sea especially in vastness
a sea of faces
4
: the seafaring life
5
: mare entry 2
at sea
to sea
1
: on the sea
specifically
: on a sea voyage
2
: lost, bewildered
: to or on the open waters of the sea
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Merriam-Webster unabridged
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Time Traveler for sea
The first known use of sea was before the 12th century
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