/in"di kay'teuhr/ , n.
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.
5. Chem.
a. a substance, as litmus, that indicates the presence or concentration of a certain constituent.
b. a substance often used in a titration to indicate the point at which the reaction is complete.
6. Ecol. a plant or animal that indicates, by its presence in a given area, the existence of certain environmental conditions.
[ 1660-70; indicator, equiv. to L indica ( re ) to INDICATE + -tor -TOR ]