\Py*rom"e*ter\, n. [Pyro- + -meter: cf. F.
pyrom[`e]tre.]
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.
Note: 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.