a device, including a relay actuated by thermal conduction or convection, that functions to establish and maintain a desired temperature automatically or signals a change in temperature for manual adjustment.
verb (used with object), thermostatted or thermostated; thermostatting or thermostating.
British Dictionary definitions for thermostatically
a device that maintains a system at a constant temperature. It often consists of a bimetallic strip that bends as it expands and contracts with temperature, thus breaking and making contact with an electrical power supply
a similar device that actuates equipment, such as a sprinkler, when a certain temperature is reached
(thûr'mə-stāt') A device that automatically controls heating or cooling equipment in such a way as to maintain a temperature at a constant level or within a specified range, generally using a thermometer capable of triggering electrical switches that activate or deactivate the equipment.