Description of the sea surface with regard to wave action. Also called state of sea.
A description of the properties of sea surface waves at a given time and place.
This might be given in terms of the wave spectrum, or more simply in terms of the significant wave height and some measure of the wave period.
Sea State has been defined 4 different ways in documents like Glossary of Coastal Terminology, Department of Defense Dictionary of Military and Associated Terms, Coral Reef Information System Glossary, and 1 more.