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to swell; to rise; to bulge; to be piled up
to rouse; to get excited
ライブ会場が盛りあがると観客が一斉に立ち上がる。
When the concert venue gets lively, the audience all stand up at once.
新商品の発表会が盛りあがるよう演出を考えた。
We planned the staging so that the new product launch would be exciting.
話題が盛りあがるにつれて時間を忘れてしまった。
As the conversation grew livelier, I lost track of time.