This is the 7245th most frequent Japanese word.
不合理
"Unreasonable" or "irrational."
In this sentence, "不合理" is used to describe the characteristic of the rule being unreasonable or illogical.
この規則は不合理だと思います。
I think this rule is unreasonable.
Here, "不合理" is used to indicate that the thought process is perceived as lacking reason or rationality.
彼の考え方は不合理に感じられる。
His way of thinking feels unreasonable.
This sentence employs "不合理" to denote the concept of basing decisions on unreasonable premises.