Any cooling which is done naturally through dissipating heat through the surrounding air. This may or may not use a heatsink.
A process whereby cold well water (less than 50° F.) is pumped directly to a finned air coil (much like the radiator of a car) so that when the heat pump fan is operated, cooling and dehumidification are provided without the operation of a compressor driven refrigeration system.
Using an ice pack or other commercial cold therapy product to cool soft tissues. (Opposite of Active Cooling which involves circulating water.)
The use of painting, shading, reflectors and other techniques to cool a spacecraft.
The method of cooling where only a heatsink is used. Nothing is used to force air over the heatsink to cool it. Most people who choose to use passive cooling are looking for a silent configuration.
A process whereby a secondary refrigerant is pumped directly to a evaporator and cooling is accomplished without a the operation of a mechanically driven refrigeration system.