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suddenly; in a flash; quickly; rapidly; swiftly; nimbly
conspicuously; prominently; showily; attractively; impressively
花火がぱっと開いた。
The fireworks burst open.
ぱっと見て分かります。
You can understand at a glance.
彼女の顔がぱっと明るくなる。
Her face suddenly brightened up.