Real Dictionary

heat pump in American English
a device for cooling or warming an enclosed space by removing heat from interior air and transferring it out, or by absorbing heat from outdoor air, or from a hot-water source, and transferring it in
noun: a device that uses a compressible refrigerant to transfer heat from one body, as the ground, air, or water, to another body, as a building, with the process being reversible

heat pump in British English
noun: a device, as used in a refrigerator, for extracting heat from a source and delivering it elsewhere at a much higher temperature

heat pump in Mechanical Engineering
noun: A heat pump is a device for taking heat from a place and delivering it to another place at a much higher temperature.