(loosely) The United Kingdom. / The island of Great Britain, consisting of England, Scotland and Wales, especially during antiquity. / (historical) Brittany. / (in the plural) The British Isles.

(obsolete) Briton; British.

(now rare, historical) An ancient Briton.

plural of Britain

(rare) Someone from Great Britain.

(historical or loosely) England and Wales.

(informal, derogatory) Britain (viewed as a crime-ridden state where society and common sense have failed)

(historical) A series of air engagements between the British Royal Air Force (RAF) and the German Luftwaffe during World War II for air superiority over southern England and the English Channel prior to any German invasion of the British Isles.

The north part of Britain, formerly specifically (now historical) Scotland.

The island (and sometimes including some of the surrounding smaller islands) off the north-west coast of Europe made up of England, Scotland, and Wales. Abbreviation: GB.