What is the meaning of the idiom " A black sheep"?

An unlucky person An ugly person A lucky person Disreputable member of a family

Disreputable member of a family

The correct answer is Disreputable member of a family. The other options are incorrect. An unlucky person does not match the meaning of the idiom. An ugly person does not match the meaning of the idiom. A lucky person does not match the meaning of the idiom.