1.
immorality, corruption, moral transgression
The act of going against moral principles or ethics. Implies a willful turning away from accepted moral standards. Often carries a literary or dramatic tone, and can suggest a forbidden allure or the thrill of transgression.
Usage
A literary and formal term. Often used with 的 to form the na-adjective 背徳的 (immoral). Frequently appears in literature, film criticism, and discussions of taboo topics. Carries a more dramatic, almost aesthetic nuance compared to the plain 不道徳 (immoral), sometimes suggesting a seductive quality to the transgression.
Etymology
背 (to turn one's back on) + 徳 (virtue, morality). Literally "turning one's back on virtue."