godan verb (-ru), intransitive verb
lose enthusiasm; become subdued; have one's excitement dampened
Colloquial intransitive verb describing a situation or mood that was lively but then loses energy; often used for parties, conversations, or group excitement. Antonym: 盛り上がる.
Antonyms: 盛り上がる (もりあがる)
When he told a boring story, the mood instantly fell flat.
盛り下がらないように、面白い話題を探そう。
Let's find an interesting topic so the excitement doesn't die down.