Py‐rom″e‐ter (?), n. [Pyro- + -meter: cf. F. pyromètre.] 1. (Physics) An instrument used for measuring the expansion of solid bodies by heat.
2. (Physics) An instrument for measuring degrees of heat above those indicated by the mercurial thermometer.
☞ It is usually constructed so as to register the change which the heat to be measured produces in the length of some expansible substance, as a metallic rod, or in the intensity of a thermo-electric current.