Most smouldering refers to something that is burning slowly and giving off smoke or heat. Antonyms for this phrase could include cool, calm, peaceful, extinguished or quenched. Cool denotes the absence of heat or warmth, while calm refers to a state of tranquillity or serenity. Peaceful pertains to a state of calmness, freedom from disturbance, and harmony. On the other hand, extinguished and quenched mean that a fire has been put out or that something is no longer burning. These antonyms are useful to express the opposite of something that is hot, burning, or causing a disturbance.