胸むな糞くそが悪わるい

also: むねくそがわるい

Meanings

1

expression, i-adjective

Strong visceral disgust, as if something turns your stomach. Often used for morally repugnant situations or extreme unpleasantness. Colloquial and somewhat vulgar due to 糞.

あの事じ件けんの詳しょう細さいを聞きいて、胸むな糞くそが悪わるくなった。
Hearing the details of that incident made me sick to my stomach.

彼かれの差さ別べつ的てきな発はつ言げんには本ほん当とうに胸むな糞くそが悪わるい。

His discriminatory remarks are truly revolting.

Written forms

胸糞が悪い
- むなくそがわるい
  Standard kanji-kana mixed spelling. The reading むなくそがわるい is the most common pronunciation.
- むねくそがわるい
  Alternate reading むねくそがわるい is occasionally heard but much less common than むなくそ.
胸くそが悪い
- むなくそがわるい
  Variant with 糞 in kana. Less common but still used.
- むねくそがわるい
むねくそがわるい

Kanji

胸bosom, breast, chest
糞shit, feces, excrement
悪bad, vice, rascal

Similar words

気き持もち悪わるい
気持ち悪い is a general term for feeling unwell or creeped out, while 胸糞が悪い specifically conveys a gut-level disgust, often with moral indignation.
吐はき気けがする
吐き気がする means 'to feel nauseous' and can be physical or metaphorical, but 胸糞が悪い is more emotionally charged and vulgar.

Etymology

Compound of 胸 (chest) + 糞 (feces) + が悪い (is bad). The image is of something so disgusting it feels like feces in your chest. The exact origin is uncertain, but it is a vivid colloquial expression.