a mechanical device that pumps and oxygenates blood: it is used during open-heart surgery, lung surgery, etc. to divert the patient's blood around the heart and lungs
See heart-lung machine in American Heritage Dictionary 4
noun
An apparatus through which blood is temporarily diverted, especially during heart surgery, to oxygenate it and pump it throughout the body, thus maintaining circulation until the heart and lungs are able to return to normal functioning.