Calefactive is a word that describes something that gives off heat or has a warming effect. Some antonyms (opposites) for calefactive could be words like cooling, refreshing, or chilling. These words describe something that has a cooling effect or reduces heat, rather than increasing or maintaining it. Other antonyms could include frigid, icy, or wintry, which describe a lack of heat or cold temperatures. Another antonym could be arctic, which suggests something that is extremely cold. These antonyms provide alternative ways to describe temperature or heat, and offer a contrast to the calefactive quality of things.