Roar is a word that refers to a loud, deep, and aggressive sound that animals or machines make. However, there are several synonyms for this word, which can add flavor to your writing or speech. For instance, "bellow" is a synonym for a deep, guttural roar that is usually associated with large animals or humans. Another synonym is "thunder," which is often used to describe the sound of a group of animals, such as a herd of elephants or a pack of lions roaring at the same time. Finally, "ruckus" is a synonym for a loud, chaotic, and disruptive noise that could be a rough equivalent to "roar".