The term "lung buster" is often used to describe physically demanding activities that require significant effort and stamina, and it is frequently used in sports and fitness contexts. Some synonyms for this term could include "breath taker," "challenging," "grueling," "strenuous," "exhausting," and "demanding." These words convey the same idea of an activity that requires serious effort and can leave a person feeling breathless, tired, and physically drained. Whether you're running a marathon, climbing a mountain, or doing a high-intensity workout, these synonyms can help convey the intensity of the experience and the need for mental and physical fortitude to keep going.