Definition of main noun from the Oxford Advanced Learner's Dictionary

     

    main

     noun
    noun
    BrE BrE//meɪn//
     
    ; NAmE NAmE//meɪn//
     
    House equipment
     
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  1. 1[countable] a large pipe that carries water or gas to a building; a large cable that carries electricity to a building a leaking gas main see also water main See related entries: House equipment
  2. 2a large pipe that carries waste water and sewage (= human waste, etc.) away from a building See related entries: House equipment
  3. 3the mains [uncountable, plural] (British English) the place where the supply of water, gas or electricity to a building or an area starts; the system of providing gas, water and electricity to a building or of carrying it away from a building The house is not yet connected to the mains. The electricity supply has been cut off at the mains. Plug the transformer into the mains (= the place on a wall where electricity is brought into a room). mains gas/water/electricity The shaver will run off batteries or mains. mains drainage
  4. Word Origin Middle English: from Old English mægen ‘physical force’, reinforced by Old Norse meginn, megn ‘strong, powerful’, both from a Germanic base meaning ‘have power’.Extra examples Some of the remoter houses in the town are not on the mains. The main serves four towns. There’s a burst water main in Quarry Road. They’re laying a new gas main through the town. Turn the water off at the mains. an island without mains electricity water damage from broken mains The area was evacuated after the discovery of a leaking gas main.Idioms used to say that a statement is true in most cases The service here is, in the main, reliable. In the main, the money raised goes to children’s charities.
See the Oxford Advanced American Dictionary entry: main