noun
bitter-tasting bug; imaginary bug that tastes bitter
Refers to an imaginary insect with a bitter taste. Almost exclusively used in the set phrase 苦虫を噛み潰したよう (like biting a bitter bug), describing a sour, disgusted, or grimacing facial expression. The word itself is rarely used outside this idiom.
See also: 苦虫を噛み潰したよう (にがむしをかみつぶしたよう)
彼は苦虫を噛み潰したような顔で、その知らせを聞いた。
He heard the news with a look on his face as if he had bitten into a bitter bug.
「苦虫」という言葉は、実際の虫ではなく、苦い味のする想像上の虫を指す。
The word 苦虫 refers not to a real insect but to an imaginary bug that tastes bitter.