Source : Webster's Revised Unabridged Dictionary (1913)

Thermobarometer \Ther`mo*ba*rom"e*ter\, n.
   A siphon barometer adapted to be used also as a thermometer.

Thermobarometer \Ther`mo*ba*rom"e*ter\, n. [Thermo- +
   barometer.] (Physics)
   An instrument for determining altitudes by the boiling point
   of water.