Thermostat
Pronunciation : Ther"mo*stat
Part of Speech : n.
Etymology : [Thermo- + Gr. (Physics)
Definition : Defn: 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.
Source : Webster's Unabridged Dictionary, 1913