stomach acid that comes up into the mouth; acid reflux fluid
Refers to the sour fluid that rises from the stomach due to acid reflux. Most commonly encountered in the idiomatic expression 虫酸が走る (むしずがはしる), meaning 'to be disgusted' or 'to make one's skin crawl'.
See also: 虫唾が走る
It's a story that makes my stomach turn.
胸やけで虫酸が上がってきた。
I had heartburn and stomach acid came up into my mouth.
逆流性食道炎 is the medical term for gastroesophageal reflux disease (GERD), the condition that causes 虫酸.
Standard kanji spelling for this word.
Alternate kanji spelling; 唾 means saliva, fitting the meaning.
Mixed kanji-kana spelling; less common.
Compound of 虫 (mushi, 'bug, worm') and 酸 (su, 'acid'). The exact origin is uncertain, but it likely refers to the sour, unpleasant sensation likened to a bug or worm in the stomach.