expression, godan verb (-ru)
feel dispirited; feel discouraged
Describes a state of feeling down, demotivated, or in low spirits, often due to circumstances or mood.
雨が続くと気が腐る。
When it keeps raining, I feel dispirited.
仕事がうまくいかなくて気が腐っている。
Work isn't going well, and I'm feeling discouraged.
Literally means 'to rot' or 'to spoil'; in 気が腐る it is used metaphorically for a depressed mood.
The expression combines 気 (spirit, mood) with 腐る (to rot), metaphorically describing a mood that has 'spoiled' or turned sour.