A lunar phase either side of the full moon when the moon's disc as seen from the Earth is larger than a semicircle.(noun)
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Use "gibbous moon" in a sentence
"A gibbous moon slid filaments of eerie silver light through the slats of the shutters, and this conspired with the energetic carpentry of the crickets to keep her lying on her back with her eyes wide open."
"Here, so far away, the night was calm, the sky full of radiance, the temperature at last bearable, and a sliver of gibbous moon let low gleam smear the southern hemisphere."