(geology, oceanography) A hemispheric-scale long but narrow topographic depression of the seabed.

(nautical) Designed and equipped to be capable of sailing on an ocean.

A proposed common ancestor of the group of Oceanic languages.

(nautical) a narrow-beam passenger ship designed for high speed trans-oceanic travel

plural of ocean liner

The act of disposing of waste (especially nuclear waste) in a deep section of the ocean.

A type of aquaculture, used mainly in culturing Pacific salmon, wherein juvenile fish are hatched and reared, released to mature in the open ocean, and caught when they return as adults to spawn.

(idiomatic) A very small or insignificant amount; something of little importance.

(obsolete or dialectal, Scotland) North Sea

(figuratively) To undertake an overwhelmingly difficult task or approach to a problem.