1. 不诚实的人；无赖；恶棍
If someone calls a man a knave, they mean that he is dishonest and should not be trusted.

2. （纸牌游戏中jack的另一种说法）
In card games, knave is another word for jack.

1. one of four face cards in a deck bearing a picture of a young prince

Synonym: jack

2. a deceitful and unreliable scoundrel

Synonym: roguerascalrapscallionscalawagscallywagvarlet