expression, ichidan verb
feel relieved; get satisfaction; vent one's frustration
Idiomatic expression literally meaning 'to lower one's sour stomach'. Used when a person feels a sense of relief or satisfaction after resolving a frustrating situation, often by taking action or seeing justice done. Typically used in the form 溜飲が下がる (intransitive) or 溜飲を下げる (transitive).
彼の謝罪を聞いて、ようやく溜飲が下がった。
Hearing his apology, I finally felt relieved.
長年の恨みを晴らして溜飲を下げた。
I settled an old grudge and felt a sense of satisfaction.