indicator in Wingdings is ♓︎■︎♎︎♓︎♍︎♋︎⧫︎□︎❒︎

A pressure gauge; a water gauge, as for a steam boiler; anapparatus or instrument for showing the working of a machine ormoving part; as:(a) (Steam Engine) An instrument which draws a diagram showing thevarying pressure in the cylinder of an engine or pump at every pointof the stroke. It consists of a small cylinder communicating with theengine cylinder and fitted with a piston which the varying pressuredrives upward more or less against the resistance of a spring. Alever imparts motion to a pencil which traces the diagram on a cardwrapped around a vertical drum which is turned back and forth by astring connected with the piston rod of the engine. See Indicatorcard (below).(b) A telltale connected with a hoisting machine, to show, at thesurface, the position of the cage in the shaft of a mine, etc.