n. The act of refrigerating or cooling; the abatement of heat; the state of being cooled.n. Specifically The operation of cooling various substances by artificial processes.n. In a broader sense, a process of refrigeration in which the cycle of heat-changes is only partly produced by mechanical action, as in compression ice-machines using anhydrous ammonia, wherein the cooling of the vapor takes place entirely during the formation from the liquid, and is caused by absorption of the latent heat of vaporization from the sensible heat of the substance, the mechanical part of the process being wholly confined to compressing the ammonia-vapor while liquefying it under the action of cold and pressure. Such machines are the most effective and the most extensively used.