big

big Big Apple an informal name for New York City.
big bang the explosion of dense matter which according to current cosmological theories marked the origin of the universe. In the beginning a fireball of radiation at extremely high temperature and density, but occupying a tiny volume, is believed to have formed. This expanded and cooled, extremely fast at first, but more slowly as subatomic particles condensed into matter which later accumulated to form galaxies and stars. The galaxies are currently still retreating from one another. What was left of the original radiation continued to cool and has been detected as a uniform background of weak microwave radiation.

In the UK, Big Bang is the name given to the introduction in 1986 of major changes in trading in the Stock Exchange, principally involving widening of membership, relaxation of rules for brokers, and computerization.
Big Ben is the great clock tower of the Houses of Parliament in London and its bell, named after Sir Benjamin Hall (1802–67), commissioner of public works at the time of its construction; Big Ben was designed by the English lawyer and mechanician Edmund Beckett, Lord Grimthorpe (1816–1905).
Big Bend National Park a US national park in a bend of the Rio Grande, in the desert lands of southern Texas on the border with Mexico, in which were discovered, in 1975, fossil remains of the pterosaur.
Big Brother a person or organization exercising total control over people's lives, from the head of state in George Orwell's novel 1984 (1949); his apparently benevolent but actually ruthlessly omnipotent rule is summed up by the slogan, ‘Big Brother is watching you.’

In 2000, Big Brother became the name of a television game show in which selected contestants shared a house and were monitored by video camera. Each week one person was voted out of the house by the viewing public, and the winner was the last contestant to remain.
big cheese an important person. The phrase dates from the 1920s, and cheese probably comes via Urdu from Persian čīz ‘thing’; the cheese was used earlier to mean ‘first-rate’ (i.e. the thing).
big fish eat little fish the rich and powerful are likely to prey on those who are less strong, and often used with the implication that each predator is in turn victim to a stronger one. Recorded from the late 12th century.
big fleas have little fleas upon their backs to bite them, and little fleas have lesser fleas, and so ad infinitum every apparently strong person is fed on and irritated by those who are weaker, and that they in turn have their own parasites. The saying comes originally from Jonathan Swift's ‘On Poetry’ (1733).
Big Smoke an informal term for London; also called the Smoke.
big stick a display of force or power, especially in international diplomacy; the phrase is associated particularly with Theodore Roosevelt (1858–1919), who recommended, ‘walk softly, and carry a big stick.’
big tent used in reference to a political party's policy of permitting or encouraging a broad spectrum of views among its members. The big tent is recorded from the 1990s as a slogan used by the American Republican Party.
big white chief an important person, the senior member of a group; the name is a humorous one modelled on the supposed speech of American Indians.

See also bigger, a big fish in a small pond, the big picture.