NOUN (1)

1. an apparatus for sending telegraphic messages by using a mirror to turn the sun's rays off and on;


VERB (1)

1. signal by means of a mirror and the using the sun's rays;

The Collaborative International Dictionary of English v.0.48:

Heliograph \He"li*o*graph\ (h[=e]"l[i^]*[-o]*gr[.a]f), n.
   [Helio- + -graph.]
   [1913 Webster]
   1. A picture taken by heliography; a photograph.
      [1913 Webster]

   2. An instrument for taking photographs of the sun.
      [1913 Webster]

   3. An apparatus for telegraphing by means of the sun's rays.
      See Heliotrope, 3.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Heliograph \He"li*o*graph\ (h[=e]"l[i^]*[-o]*gr[.a]f), v. t.
   1. To telegraph, or signal, with a heliograph.
      [Webster 1913 Suppl.]

   2. To photograph by sunlight.
      [Webster 1913 Suppl.]

WordNet (r) 3.0 (2006):

heliograph
    n 1: an apparatus for sending telegraphic messages by using a
         mirror to turn the sun's rays off and on
    v 1: signal by means of a mirror and the using the sun's rays