What does OS stand for?

Office of The Secretary

Operations Security

Systematic and proven process by which potential adversaries can be denied information about capabilities and intentions by identifying, controlling, and protecting generally unclassified evidence of the planning and execution of sensitive activities.

Operating Strength

Office of Scheduling

Own Ship

In ECDIS a term identifying the vessel upon which an ECDIS is operating.

Oxidative Stress

Mouth

The nautical mile (symbol M, NM or nmi) is a unit of length that is approximately one minute of arc measured along any meridian. By international agreement it has been set at 1,852 metres exactly (about 6,076 feet).

O'Clock Shadow

Oxide Semiconductor