black (adj.) not allowed by law黑市的，非法交易的
black market (n.) a situation of illegal trading in goods, currencies or services黑市
[例] He bought some pirate CDs on the black market.
in the black in credit（银行存款）有赢余
black list list of goods, companies, people who are prohibited from trading黑名单
[例] The customer is in the system black list so we can not provide trading service for him.
