From Longman Dictionary of Contemporary Englishpilot lightˈpilot light noun [countable] TPGa small gas flame that burns all the time and is used for lighting larger gas burners
Examples from the Corpus
pilot light• A pilot light on the tank's control panel conveniently lets you know when the iron is running out of steam.• The blue pilot light glowed behind the window of the central-heating boiler but the pump was switched off.• The comforting blue flame of the pilot light was dead, blown out by the gusting wind of the night before.• Still swearing under his breath, Dexter pulled off the cover from the bottom of the boiler and relit the pilot light.• A tiny pilot light, if you like, that was necessary to set everything else in motion. 