noun Physics.

- the amount of heat required to raise the temperature of 1 pound (0.4 kg) of water 1°F. Abbreviation: Btu, BTU, B.t.u., B.T.U., B.th.u.

noun

- a unit of heat in the fps system equal to the quantity of heat required to raise the temperature of 1 pound of water by 1°F. 1 British thermal unit is equivalent to 1055.06 joules or 251.997 caloriesAbbrevs: btu, BThU

n.

- The quantity of heat required to raise the temperature of one pound of water from 60° to 61°F at a constant pressure of one atmosphere.
- The quantity of heat equal to 1180 of the heat required to raise the temperature of one pound of water from 32° to 212°F at a constant pressure of one atmosphere.

- A unit used mainly to measure heat but also applied to other forms of energy. One British thermal unit is equal to the amount of heat needed to raise the temperature of one pound of water by one degree Fahrenheit, or 251.997 calories.

A unit for measuring heat. One Btu raises the temperature of one pound of water one degree Fahrenheit (see also Fahrenheit).