1A subdivision of a state, nation, country, etc.; a subsidiary state, territory, etc., within a larger political entity, with varying degrees of autonomy depending on the context.
2A state of existence regarded as a subdivision or component of another state; (Physics ) a quantum state that is a subdivision of a more broadly defined state.
Origin
Early 19th century; earliest use found in Louisville (Kentucky) Public Advertiser. From sub- + state.