猫腻 (māonì) secrete, underhanded activity; ignoble trick

Usage:

“猫腻”是北京方言，指隐秘的活动，尤其指不为众人所知的、不光彩的事情。
“猫腻” is a local Beijing saying. It means underhanded activity, especially a secretive or ignoble trick.

Sentences:

1、Jiǎ: Zhēn dǎoméi! Wǒ mǎidào le jiǎhuò.
甲：真倒霉！我买到了假货。
A: What bad luck! I bought a fake.

Yǐ : Zhème piányi, yīdìng yǒu māonì a.
乙：这么便宜，一定有猫腻啊。
B: It was so cheap; of course it’s an ignoble trick.

2、Jiǎ: Wǒmen zǒng shūqiú, wǒ huáiyí shìcáipàn chuī hēishào.
甲：我们总输球，我怀疑是裁判吹黑哨。
A: We always lose our matches. I suspect the referee is deliberately making bad calls.

Yǐ : Zhè qízhōng de māonì jìu bùdé’ érzhī le.
乙：这其中的猫腻就不得而知了。
B: We’ll never know about this underhanded activity.

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