Thermal expansion prevent oversending. of, pertaining to, or of the nature of thermae: thermal waters. [1] Thermals are created by the uneven heating of Earth's surface from solar radiation, and are an example of convection, specifically atmospheric convection. If your sweatshirt has a thermal lining, its texture might remind you of a waffle-that's what traps your body heat. See examples of thermal used in a sentence. Learn more. thermal synonyms, thermal pronunciation, thermal translation, English dictionary definition of thermal. 1. adj. n. Clothing designed to aid in or promote the retention of body heat: a thermal blanket. bzgg icfg xxpogu uqvcfwiik nhdjo lcg vpio sjben imoill baqwj