Utter madness is a phrase often used to describe something that is completely irrational or insane. There are several synonyms that can be used to convey the same meaning, such as absolute lunacy, sheer insanity, total chaos, complete mayhem, and absolute bedlam. These words can be used interchangeably depending on the context in which they are being used. For instance, if describing a chaotic scene or situation, words like bedlam or mayhem would be appropriate. On the other hand, if trying to convey the idea of complete irrationality, the words like lunacy and insanity would be more applicable. Overall, these synonyms can help add variety to one's writing while also expressing similar ideas.