Big Four means: The four top Allied powers of World War I and their leaders: David Lloyd George of Britain, Georges Clemenceau of France, Vittorio Emanuele Orlando of Italy and Woodrow Wilson of the United States,. The word is mostly archaic or historical; you will only encounter it in old texts, period drama, or school history rather than current teen conversation. There is no real cause for parental concern; it is descriptive vocabulary rather than risky behaviour.