Source : Webster's Revised Unabridged Dictionary (1913)

Thermoregulator \Ther`mo*reg"u*la`tor\, n. (Physics)
   A device for the automatic regulation of temperature; a
   thermostat.

Source : WordNet®

thermoregulator
     n : a regulator for automatically regulating temperature by
         starting or stopping the supply of heat [syn: {thermostat}]