Definition of heliograph noun from the Oxford Advanced American Dictionary

     

    heliograph

     noun
    noun
    NAmE//ˈhiliəˌɡræf//
     
     
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  1. 1a device that gives signals by reflecting flashes of light from the sun
  2. 2(also heliogram
    NAmE//ˈhiliəˌɡræm//
     
    )
    a message that is sent using signals from a heliograph
  3. 3a special camera that takes photographs of the sun
See the Oxford Advanced Learner's Dictionary entry: heliograph