Untremulous is an adjective that is used to describe someone who is calm, steady and not shaking or quivering. Some synonyms for untremulous include unperturbed, unflappable, composed, collected, unshaken, unwavering and imperturbable. These words convey the same meaning as untremulous and can be used interchangeably depending on the context. For instance, if you want to describe someone who is unfazed by an unexpected event, you can say they are unperturbed or unflappable. Similarly, if you want to describe someone who remains calm under pressure, you can use the words composed, collected or imperturbable to convey the same idea.