■ noun
1》 a signalling device by which sunlight is reflected in flashes from a movable mirror.
↘a message sent by ~; a heliogram.
2》 a telescopic apparatus for photographing the sun.
3》 historical a type of early photographic engraving made using a sensitized silver plate and an asphalt or bitumen varnish.
■ verb
1》 send (a message) by ~.
2》 take a ~ic photograph of.
Derivatives
~ic adjective
~y noun