improper; inappropriate; unfair
Used for actions, methods, or conditions that are not proper, not suitable, or not fair according to rules, standards, or ethics. Often appears in formal or official contexts.
The contract contains improper clauses.
不適正な会計処理が発覚した。
Inappropriate accounting practices were uncovered.
不当 means 'unjust' or 'unreasonable', focusing on unfairness; 不適正 is broader, covering impropriety and unsuitability as well.
Compound of 不 (negative prefix) + 適正 (proper, appropriate). The word 適正 itself is a combination of 適 (suitable) and 正 (correct).