- The definition of a thermometer is a tool used to measure temperature.
An example of a thermometer is a little stick with mercury in it that tells you how hot it is outside or how high your fever is.
- an instrument for measuring temperatures, consisting of a graduated glass tube with a sealed, capillary bore in which mercury, colored alcohol, etc. rises or falls as it expands or contracts from changes in temperature
- any similar instrument, as one operating by means of a thermocouple
Origin of thermometerFrench thermomètre: see thermo- and amp; -meter
- An apparatus used to measure temperature.