One of the larger bodies of salt water, less than an ocean, found on the earth's surface; a body of salt water of second rank, generally forming part of, or connecting with, an ocean or a larger sea; as, the Mediterranean Sea; the Sea of Marmora; the North Sea; the Carribean Sea.
- The continuous body of salt water covering most of the earth's surface, especially this body regarded as a geophysical entity distinct from earth and sky.
- A tract of water within an ocean.
- A relatively large body of salt water completely or partially enclosed by land.
- A relatively large landlocked body of fresh water.
- The condition of the ocean's surface with regard to its course, flow, swell, or turbulence: a rising sea; choppy seas.
- A wave or swell, especially a large one: a 40-foot sea that broke over the stern.
- Something that suggests the ocean in its overwhelming sweep or vastness: a sea of controversy.
- Seafaring as a way of life.
- Astronomy A lunar mare.
- at sea On the sea, especially on a sea voyage.
- at sea In a state of confusion or perplexity; at a loss.