Refers to a lack of moral integrity or ethical conduct, often in personal or social behavior. Slightly formal and not extremely common in everyday speech.
His immoral conduct was criticized.
You must not commit dishonest acts.
不正 focuses on injustice, unfairness, or illegality, whereas 不徳義 emphasizes moral failing or dishonesty in personal conduct.
Compound of 不 (not) + 徳義 (morality, integrity). The exact historical derivation is uncertain, but the word follows a common pattern of negating a moral concept.