Pronunciation: (hē'lē-u-graf", -gräf"),[key] —n. 1. a device for signaling by means of a movable mirror that reflects beams of light, esp. sunlight, to a distance.
3. Meteorol.an instrument for recording the duration and intensity of sunshine.
4. Photog.,Print.an early type of photoengraving made on a metal plate coated with sensitized asphalt.