More seething is a phrase commonly used when someone is feeling intense anger or frustration. If we were to look for antonyms of this phrase, we would need to find words that convey the opposite meaning. Calm, peaceful, and composed could be considered antonyms of seething as they represent tranquillity and a sense of control. Serene, placid, and tranquil are some other antonyms that are often used to describe a peaceful state of being. If a person is not seething, they may be content, satisfied, or even elated. So, when we look for antonyms for more seething, we are essentially looking for words that represent the opposite of anger and agitation.