(automotive) A turn signal or indicator. / (aviation) An instrument that shows both the current heading and the desired heading needed to follow a predetermined course.

Any device for comparing a physical property of two objects, or an object with a standard.

A float used by anglers to tell when a fish has taken the bait

plural of leading indicator

A phenomenon that generally occurs in advance of a more important phenomenon, aiding in its prediction.

(aviation) A two-letter indicator used in fare construction to indicate the basic routing that the fare applies to.

(chemistry) A substance that exists in an oxidized and reduced forms, these forms having different colours, changing colour at a specific redox potential

(rail transport) A panel attached to a colour light signal situated just before a junction, which when lit up indicates that a diverging route has been set for the next train.

plural of route indicator

(Internet) A symbol conveying the tone or context of a message.