The term 'BIG REALM' can be broken down into two crossword solutions: EMPIRE (6 letters) and REALM (5 letters). An EMPIRE is a large political unit with a single ruler, usually an emperor or empress. Empires have existed throughout history, from the ancient empires of Egypt, Greece, and Rome to the modern empires of the United States, China, and Russia. A REALM is a kingdom or domain, often referring to a monarchy or other form of government. Realms are typically larger than a single country, and may include multiple countries or regions.