Respiratory heart is a term used to describe an organ that plays a crucial role in both the respiratory and circulatory systems. However, there are various synonyms that can be used to refer to this important organ. The most commonly used synonym is "lung-heart", as it highlights the dual functioning of the organ. Another synonym that is often used is "pulmonary cardiac system", which emphasizes the relationship between the heart and lungs. Additionally, "breathing pump" is a simpler synonym that focuses on the heart's role in pumping oxygenated blood throughout the body. In conclusion, these synonyms effectively convey the concept of the respiratory heart and its functions within the body.