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 calories
Abbrevs: btu, BThU
thermal unit in American English
noun
a unit of heat energy or of the equivalent of heat energy in work
Word origin
[1875–80]This word is first recorded in the period 1875–80. Other words that entered Englishat around the same time include: graph, knockabout, massage, musical chairs, overdraft
Examples of 'thermal unit' in a sentence
thermal unit
An estimated 800,000 homes have solar photovoltaic panels, which produce electricity from the sun, and 200,000 have solar thermal units to provide hot water.