'Wrongful' describes an action taken against someone that should never have been taken — it was unfair, or against the law, and the person it happened to had done nothing to deserve it.

It is almost a legal word, and it sits in front of a small set of nouns you should learn as fixed pairs: wrongful arrest, wrongful dismissal (BrE) or wrongful termination (AmE, losing your job unfairly), wrongful conviction (found guilty when you were innocent), wrongful imprisonment, wrongful death. Outside these set phrases it sounds strange, so do not use it as a general word for 'bad'.

Here is the part that surprises students: 'wrongful' looks at the ACT DONE TO the person, and quietly says the person was innocent. Compare 'wrong' — you can do something wrong yourself. Nobody says 'I did a wrongful thing'; you say 'I did something wrong'. 'Wrongful' points the finger at the police, the boss, the court — the side with power that used it badly.

Because of that, the word usually appears where money and courts are involved: someone was treated unlawfully, and now they are suing. You will meet it far more often in the news and in contracts than in conversation.