The Collaborative International Dictionary
Pilot lamp
Pilot lamp \Pilot lamp\ or Pilot light \Pilot light\ (Elec.)
A small incandescent telltale lamp on a dynamo or battery circuit to show approximately by its brightness the voltage of the current.
a small light on an electrical device to indicate whether the device is in operation or that the power is on.
WordNet
pilot lamp
n. indicator consisting of a light to indicate whether power is on or a motor is in operation [syn: pilot light, indicator lamp]