Chinese idioms：自相矛盾(Zìxiāngmáodùn)

Hěnjiǔ hěnjiǔ yǐ qián, Chǔ guó yǒu yí gè shāngrén, yì tiān tā dào shìchǎng shàng qù mài zìjǐ zhìzào de máo hé dùn. Tā dà shēng de jiào mài, yǒu hěn duō rén wéiguò lái kàn, tā jǔ qǐ dùn shuō:” wǒ de dùn shì shìjiè shàng zuì jiāngù de, wúlùn zěnyàng fēnglì de dōngxī yě bù néng cìchuān tā!” Jiē zhe, tā yòu ná qǐ yí zhī máo, dé yì dì shuō:” wǒ de máo shì shìjiè shàng zuìfēng lì de, wúlùn zěnyàng jiāngù de dōngxī yě néng cìchuān!” Zhè shí yí wèi wéiguān de rén shàng qián ná qǐ tā de yì zhī máo hé yí miàn dùn wèn dào:” rúguǒ yòng zhè zhī máo qù cì zhè miàn dùn, jiéguǒ huì zěnyàng ne?” Zhè gè rén yí xià zǐ huídá bù chūlái, zuìhòu zhī hǎo huīliūliū de káng zhe máo hé dùn zǒu le.
很久很久以前，楚国有一个商人，一天他到市场上去卖自己制造的矛和盾。 他大声的叫卖，有很多人围过来看，他举起盾说：“我的盾是世界上最坚固的，无论怎样锋利的东西也不能刺穿它!” 接着，他又拿起一支矛，得意地说：“我的矛是世界上最锋利的，无论怎样坚固的东西也能刺穿!”这时一位围观的人上前拿起他的一支矛和一面盾问道：“如果用这支矛去刺这面盾，结果会怎样呢?” 这个人一下子回答不出来，最后只好灰溜溜地扛着矛和盾走了。
once upon a time, there was a businessman in Chu State. One day, he sold his spear and shield in the market. He told people, "My spear is the sharpest spear in the world. It can pierce everything. And my shield is the solidest in the world. Nothing can destroy it." Then somebody asked him, "If we use your spear to pierce your shield, what will happen?" The businessman didn't know how to reply.

Words：
楚国chǔguó： Chu state (n.)
商人shāngrén： businessman; merchant; dealer (n. )
矛máo： lancer; spear (n. )
盾dùn： shield (n.)
坚固jiāngù：firm; solid (adj.)
锋利fēnglì：sharp(adj.)
刺穿cìchuān：cut through; pierce (v.)
得意déyì: complacent (adj. )
围观wéiguān：to be an onlooker (v.)
扛káng：lift with hands; carry on the shoulder (v.)
Meanings：
自相矛盾：比喻语言、行动前后不一致或互相抵触。
This idom means being self-contradictory.

Sentences：
1. Nǐshuō shǒujī méi diàn le, què gāng gěi tā dǎle diànhuà, zhè bú shì zìxiāngmáodùn ma?
你说手机没电了，却刚给他打了电话，这不是自相矛盾吗？
You said his cell phone ran off power but you called him just now. Isn't it Zìxiāngmáodùn?

2. Nǐ gāngcái de huà qiánhòu zìxiāngmáodùn, biéren bù zhīdào gāi zěnme líjiě.
你刚才的话前后自相矛盾，别人不知道该怎么理解。
What you said is Zìxiāngmáodùn. People don't know how to understand it.