against the rules of a religion or morally wrong

He confessed that he had sinful thoughts. 他承认曾动过邪念。

Buying that sports car was a sinful waste of money. 买那辆跑车浪费金钱，真是罪过。

used to refer to something that is very pleasant, but very bad for you

This cake is sinful! 这蛋糕很诱人！