A unit of heat equal to the amount of heat required to raise one pound of water one degree Fahrenheit at one atmosphere pressure; equivalent to 251.997 calories - British thermal unit, B.Th.U.
Noun: B.T.U.
A unit of energy equal to the work done by a power of 1000 watts operating for one hour - kilowatt hour, kW-hr, Board of Trade unit [UK], kWh