<p><strong>Noun</strong></p><ul><li>a person or thing that indicates, signals, or points out.</li><li>a pointing or directing mechanism, as a pointer on the dial of an instrument to show pressure, temperature, speed, volume, etc., or a moveable icon in the graphical user interface of a computer or other device.</li><li>an instrument that indicates the condition of a machine or the like.</li><li>an instrument for measuring and recording variations of pressure in the cylinder of an engine.</li><li>a substance, as litmus, that indicates the presence or concentration of a certain constituent.</li><li>a substance often used in a titration to indicate the point at which the reaction is complete.</li><li>a plant, animal, or species that indicates, by its presence in a given area, the existence of certain environmental conditions.</li></ul>