The Collaborative International Dictionary of English v.0.48:

Generator \Gen"er*a`tor\, n. [L.]
   1. One who, or that which, generates, begets, causes, or
      produces.
      [1913 Webster]

   2. An apparatus in which vapor or gas is formed from a liquid
      or solid by means of heat or chemical process, as a steam
      boiler, gas retort, or vessel for generating carbonic acid
      gas, etc.
      [1913 Webster]

   3. (Mus.) The principal sound or sounds by which others are
      produced; the fundamental note or root of the common
      chord; -- called also generating tone.
      [1913 Webster]

   4. (Elec.) Any machine that transforms mechanical into
      electrical energy; a dynamo.
      [Webster 1913 Suppl.]

   5. (Math.) a mathematical entity which, when subjected to an
      operation, yields another mathematical entity; also, a
      generatrix.
      [PJC]

WordNet (r) 3.0 (2006):

generator
    n 1: an apparatus that produces a vapor or gas
    2: engine that converts mechanical energy into electrical energy
       by electromagnetic induction
    3: someone who originates or causes or initiates something; "he
       was the generator of several complaints" [syn: generator,
       source, author]
    4: an electronic device for producing a signal voltage