Definition of heliogram in English:

heliogram

noun

  • A message sent by reflecting sunlight in flashes from a movable mirror.

    ‘the prehistoric Indian could send his heliograms considerable distances’
    • ‘We will confirm your order by telephone, fax, email, snail mail, carrier pigeon, heliogram or a certain pattern of stones at a designated place.’

Pronunciation

heliogram

/ˈhiːlɪə(ʊ)ɡram/