Inadmissible refers to something that is not acceptable, not allowed or not permitted. There are multiple synonyms that can be used in place of this word depending upon the context, including: prohibited, disallowed, forbidden, impermissible, unsuitable, unacceptable, illegitimate, illicit, barred, illegal, inappropriate, unwarranted, unsanctioned, not allowed, and not permitted. Each of these synonyms can be used to convey the same meaning as inadmissible, but may be more appropriate in certain situations. When writing, it is important to consider the tone and context of the sentence to ensure that the correct word is chosen.