Un-intelligibly is a word used to describe speech or language that is impossible to understand. However, there are several synonyms that can be used in its place. One such synonym is incomprehensibly, which describes something that cannot be grasped or understood. Another synonym is unintelligibly, which means that something is difficult or impossible to make sense of. Additional synonyms include indistinctly, meaning unclear and lacking in clarity, and incoherently, meaning disjointed and difficult to follow. All of these terms can be used to convey the same meaning as "un-intelligibly", offering alternative word choices to express the same idea.