Definition of "brighten up" [brighten up]

• To become brighter (verb)
• To make cheerful. (verb)

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• "Stands of captured arms and armor helped to brighten up the place as well."
• "Then he got sulky, and didn't brighten up till we ran into the mouth of the Reindeer River, where a camp of Siwashes were fishing salmon."
• "By now it’s dark and the streetlights flicker on and brighten up the gray-colored road."