Ocean, n.
Etymology: [F. océan, L. oceanus, Gr.
1. The whole body of salt water which covers more than three fifths of the surface of the globe; -- called also the sea, or great sea. Like the odor of brine from the ocean Comes the thought of other years. Longfellow.
2. One of the large bodies of water into which the great ocean is regarded as divided, as the Atlantic, Pacific, Indian, Arctic and Antarctic oceans.
3. An immense expanse; any vast space or quantity without apparent limits; as, the boundless ocean of eternity; an ocean of affairs. Locke.
1 other Webster entry under this spelling
Ocean, a.
Of or pertaining to the main or great sea; as, the ocean waves; an ocean stream. Milton.
Shades of meaning
Fernald has no entry of its own for ocean; he lists it under nautical.
Where he writes about it:
Marine (L. mare, sea) signifies belonging to the ocean, maritime, a secondary derivative from the same root, bordering on or connected with the ocean; as, marine products; marine animals; maritime nations; maritime laws. — from nautical
Ocean, used adjectively, is applied to that which belongs to or is part of the ocean; oceanic may be used in the same sense, but is especially applied to that which borders on (or upon) or is connected with, or which is similar to or suggestive of an ocean; we speak of ocean currents, oceanic islands, or, perhaps, of an oceanic intellect. — from nautical