"没门儿(méi ménr)" literally means there is no door to get out. Its extended meaning is there is no possibility in doing something, indicating no room for negotiation or compromise.
例句
1、甲:你能借我点钱吗? Jiă: Nǐ néng jiè wǒ diǎn qián ma? A: Can you lend me some money?
乙:没门儿,你上次借我的钱还没还呢。 Yǐ: Méi ménr, nǐ shàngcì jiè wǒ de qián hái méiu huán ne. B: No way. You have not returned the money you borrowed last time.
2、甲:你帮我把作业写完吧? Jiă: Nǐ bāng wǒ bǎ zuòyè xiě wán ba. A: Can you help me with my homework?
乙:没门儿,自己的事情自己做。 Yǐ: Méi ménr.Zìjǐ de shìqing zìjǐ zuò. B: No way. You must rely on yourself.