na-adjective, noun
unreasonable; irrational; illogical
Archaic adjectival noun and noun. In modern Japanese, 不合理 or 理不尽 are far more common for these meanings. This word may appear in older texts or formal contexts.
古い文献では、その決定を不理と評している。
In old documents, that decision is described as unreasonable.
彼の主張は不理であると一蹴された。
His argument was dismissed as irrational.