A substance that remains a gas at low temperatures and pressure and can be used to transfer heat. Freon used in air-conditioning systems is a refrigerant.
Merriam-Webster Online Dictionary
refrigerant (adjective) allaying heat or fever
a refrigerant agent or agency as
a) a medication for reducing body heat
b) a substance used in - refrigeration
refrigerant (Wikipedia)
A refrigerant is a substance or mixture, usually a fluid, used in a heat pump and refrigeration cycle. In most cycles it undergoes phase transitions from a liquid to a gas and back again. Many working fluids have been used for such purposes. Fluorocarbons, especially chlorofluorocarbons, became commonplace in the 20th century, but they are being phased out because of their ozone depletion effects. Other common refrigerants used in various applications are ammonia, sulfur dioxide, and non-halogenated hydrocarbons such as propane.