1a thing that indicates the state or level of something:car ownership is frequently used as an indicator of affluence
2a device providing specific information on the state or condition of something, in particular:
[usually with modifier] a gauge or meter of a specified kind:a speed indicatoran altitude indicator
British a board or screen in a railway station, airport, etc. giving current information: [as modifier]:the indicator board
3British a flashing light or (formerly) other device on a vehicle to show that it is about to change lanes or turn: [as modifier]:an indicator light
4 Chemistry a compound which changes colour at a specific pH value or in the presence of a particular substance, and can be used to monitor acidity, alkalinity, or the progress of a reaction:the remaining alkali is titrated against standard acid using phenolphthalein as indicator
5 (also indicator species) an animal or plant species which can be used to infer conditions in a particular habitat:the raccoon is a poor choice as an indicator of riparian habitat
