C2 noun /ˈɒnwiː/ or /ˈɑːnwiː/
ennui
退屈
Meaning
A feeling of boredom, listlessness, or dissatisfaction arising from lack of excitement.
Example
After weeks of doing nothing, he sank into a deep sense of ennui.
何もせずに数週間後、彼は深い退屈に沈んだ。