Historical, Brit. the United Kingdom and the British dominions, colonies, etc.
See British Empire in American Heritage Dictionary 4
The geographic and political units formerly under British control, including dominions, colonies, dependencies, trust territories, and protectorates. At the height of its power in the late 19th and early 20th centuries, the empire comprised about one quarter of the world's land area and population and encompassed territories on every continent, including the British Isles, British North America, British West Indies, British Guiana, British West Africa, British East Africa, India, Australia, and New Zealand.