Poikilothermal is a scientific term that refers to organisms that have body temperatures that vary with changes in their environment. There are several common synonyms for poikilothermal, including cold-blooded, ectothermic, and heterothermic. These terms are often used interchangeably when referring to animals like reptiles, amphibians, and fish that rely on external heat sources to regulate their body temperature. Another synonym for poikilothermal is thermoregulatory, which refers to an animal's ability to maintain a constant internal body temperature despite changes in their surroundings. Whether you use poikilothermal or one of its related synonyms, it is important to understand the biological processes behind an organism's temperature regulation.