1To have one's enthusiasm or the atmosphere dampened; to become subdued. A colloquial expression for when excitement or interest lessens.
急に雨が降って、花火大会の雰囲気が盛り下がった。
It suddenly rained, and the atmosphere of the fireworks festival was dampened.
話題が暗いニュースに変わってから、会話が盛り下がってしまった。
After the topic turned to gloomy news, the conversation became subdued.
彼の一言で場が盛り下がったので、すぐに別の話題に切り替えた。
His remark dampened the mood, so we quickly switched to another topic.