矢口否认 vehemently deny
Explanation
指坚决否认，一口咬定，死不承认。
Refers to a firm denial, sticking to one's statement, stubborn denial.
Origin Story
话说唐朝时期，有一个贪官污吏叫李善，他利用职务之便，贪污受贿，搜刮民脂民膏，私下积累了大量的钱财。有一天，皇帝派御史大夫前来调查，李善害怕自己的罪行败露，便矢口否认一切指控，说自己两袖清风，清廉正直。御史大夫早已掌握了李善贪污的铁证，拿出确凿的证据，一一列举李善的罪行。面对这些铁证如山的证据，李善依然矢口否认，态度嚣张跋扈。最终，在人证物证俱全的情况下，李善的罪行被揭露，被判处了死刑。
In the Tang Dynasty, there was a corrupt official named Li Shan, who used his position for personal gain, accepting bribes, and embezzling vast sums of money. One day, the emperor sent an imperial censor to investigate. Fearing exposure, Li Shan vehemently denied all accusations, claiming to be incorruptible. However, the imperial censor had already gathered conclusive evidence of Li Shan's corruption and presented it in detail. Despite this irrefutable evidence, Li Shan continued to deny everything. Finally, with both witness testimonies and physical evidence, Li Shan's crimes were revealed, and he was sentenced to death.
Usage
主要用于口语，指坚决否认，不承认。
Mainly used in spoken language, it refers to a firm denial and non-recognition.
Examples
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面对警方的质问，他矢口否认自己参与了犯罪活动。
miàn duì jǐngfāng de zhìwèn, tā shǐkǒu fǒurèn zìjǐ cānyùle fànzuì huódòng.
He vehemently denied his involvement in the crime when questioned by the police.
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尽管证据确凿，他仍然矢口否认自己的错误，令人气愤。
jǐnguǎn zhèngjù quèzá, tā réngrán shǐkǒu fǒurèn zìjǐ de cuòwù, lìng rén qìfèn.
Despite the overwhelming evidence, he stubbornly denied his mistakes, which is infuriating.