Decalescent is a rare word that means becoming warm or hot. The antonyms for decalescent would be words that describe a decrease in temperature or coolness. Words like frigid, freezing, cold, chilly, icy, and frosty would be antonyms for decalescent. These words are often associated with winter weather or regions that experience cold temperatures. Alternatively, words that describe a lack of warmth could also be antonyms for decalescent, such as cool, tepid, lukewarm, or cold-hearted. When looking for the opposite of decalescent, it is important to consider the context in which the word is being used and choose a suitable antonym accordingly.