Antonyms for the word "tumultuous" refer to words that have the opposite meaning of tumultuous. These words could be used to describe a calming, peaceful, or orderly environment. Some of the antonyms for the word "tumultuous" include tranquil, peaceful, serene, calm, quiet, placid, stable, and steady. These words suggest a state of calm and peacefulness, rather than chaos and disorder. When used in a sentence, these antonyms can help to create a sense of relaxation and comfort. For example, "After a tumultuous day, she found solace in the tranquil beauty of the countryside.