Dictionary.net

• 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

2006 - WordNet 3.0
By Princeton University

• 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

2011 - English Dictionary Database
By DataStellar Co., Ltd