cal·o·rie (kălˈə-rē)

1. A unit of energy-producing potential supplied by food and released upon oxidation by the body, equal to the amount of energy required to raise the temperature of 1 kilogram of water by 1°C at one atmosphere pressure. Also called nutritionist's calorie.
2. The unit of heat equal to the amount of heat required to raise the temperature of 1 kilogram of water by 1°C at 1 atmosphere pressure. Also called kilocalorie, kilogram calorie, large calorie.
3. Any of several approximately equal units of heat, each measured as the quantity of heat required to raise the temperature of 1 gram of water by 1°C from a standard initial temperature at 1 atmosphere pressure. Also called gram calorie, small calorie.
4. The unit of heat equal to ¹/₁₀₀ the quantity of heat required to raise the temperature of 1 gram of water from 0 to 100°C at 1 atmosphere pressure. Also called mean calorie.