'Pilot light' definitions:

Definition of 'pilot light'

noun

Small auxiliary gas burner that provides a flame to ignite a larger gas burner [syn: pilot burner, pilot light, pilot]

noun

Indicator consisting of a light to indicate whether power is on or a motor is in operation [syn: pilot light, pilot lamp, indicator lamp]

From: GCIDE

Pilot lamp \Pilot lamp\ or Pilot light \Pilot light\ (Elec.)
1. A small incandescent telltale lamp on a dynamo or battery circuit to show approximately by its brightness the voltage of the current. [Webster 1913 Suppl.]
2. a small light on an electrical device to indicate whether the device is in operation or that the power is on. [PJC]

From: GCIDE

Pilot light \Pi"lot light`\, n. a small gas flame kept burning continuously on a stove, water heater, or other gas-burning device, so as to allow immediate ignition of the main flame when the gas flow is turned on. [PJC]