indicator: Meaning and Definition of

in•di•ca•tor

1. a person or thing that indicates.
2. a pointing or directing device, as a pointer on the dial of an instrument to show pressure, temperature, speed, volume, or the like.
3. an instrument that indicates the condition of a machine or the like.
4. an instrument for measuring and recording variations of pressure in the cylinder of an engine.
1. a substance, as litmus, that indicates the presence or concentration of a certain constituent.
2. a substance often used in a titration to indicate the point at which the reaction is complete.
6. a plant or animal that indicates, by its presence in a given area, the existence of certain environmental conditions.