Py*rom"e*ter (?), n. [Pyro- + -meter: cf. F. pyrometre.]
An instrument used for measuring the expansion of solid bodies by heat.
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.
© Webster 1913.