range light

noun nautical

one of a pattern of navigation lights, usually fixed ashore, used by vessels for manoeuvring in narrow channels at night
one of a distinctive pattern of lights shown at night on the masts of a powered vessel, such as a tugboat, to aid in identifying its size, number of barges in tow, etc

Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Examples from the Web for range light

Historical Examples of range light

The range-light emits light toward all points of the compass and must be intense enough to be seen at a distance of three miles.
Artificial Light
M. Luckiesh