When it comes to describing the absence of logic, there are several synonyms that can be used to convey the same meaning. The term irrationality refers to behaviour or thinking that is not based on reason or sound judgement. Another synonym is incoherence, which describes a lack of clarity or organization in thought or speech. Similarly, illogicality refers to a lack of logical consistency or coherence in reasoning. Nonsensical, absurd, and preposterous are other synonyms that are often used to describe situations where there is a complete absence of logic. In any case, all these synonyms essentially convey the same message: an idea or action that lacks rationality and coherence.