Ther"mo*stat (?), n. [Thermo- + Gr. &?; to make to stand.] (Physics) A self-acting apparatus for regulating temperature by the unequal expansion of different metals, liquids, or gases by heat, as in opening or closing the damper of a stove, or the like, as the heat becomes greater or less than is desired.

Ther"mo*stat (?), n. [Thermo- + Gr. &?; to make to stand.] (Physics) A self-acting apparatus for regulating temperature by the unequal expansion of different metals, liquids, or gases by heat, as in opening or closing the damper of a stove, or the like, as the heat becomes greater or less than is desired.

• a device that automatically responds to changes in temperature by activating a heating or cooling system to maintain the temperature at a desired setting