Spumescent is an adjective that describes something that is frothy or foamy. An antonym, on the other hand, is a word that means the opposite. So, what is the opposite of spumescent? Well, there are several words that could be considered antonyms for spumescent. Some examples include flat, still, calm, and placid. These words describe things that are not frothy or foamy, but instead are quiet and smooth. Other antonyms for spumescent could include settled, unagitated, stationary, and tranquil. By understanding the different antonyms for spumescent, we can better appreciate the diversity of the English language and the range of vocabulary available to us.