(chemistry) A substance that shows the acidity or alkalinity of a solution by its colour.

Third-person singular simple present indicative form of indicate

(aviation) An instrument that displays an aircraft's current airspeed.

A pointer or index that indicates something. / A meter or gauge. / The needle or dial on such a meter.

present participle of indicate

(chemistry) any substance used to classify another, often by changing colour

(aviation) An aircraft instrument that provides an indication of the vertical change in position.

plural of indication

(aviation, UK, military) An instrument that displays attitude of an aircraft in pitch and roll.

(aviation) An instrument installed in an aircraft that indicates the rate at which the aircraft is gaining or losing altitude.