Undoubtable is a word used to describe something that is without doubt or uncertainty. However, there are several synonyms that can also convey the same meaning, such as indisputable, unquestionable, certain, unmistakable, and definite. Indisputable refers to something that cannot be argued or challenged, while unquestionable implies something that is beyond doubt or suspicion. Certain suggests a high level of confidence or certitude, while unmistakable implies that something is clear and obvious. Finally, definite refers to something that is precise and unambiguous. All of these synonyms share the same idea of being truthful and undeniable, making them excellent alternatives to undoubtable.