Definition of "hollow out" []

• To make something hollow. (verb)
• To become hollow (verb)

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• "The city killer was so hugewhoever had built it wielded enough power to hollow out mountains."
• "I hollow out one of the old bolt-holes in the top to accommodate a smooth, round flattened pebble from the Hebrides, like a tiny curling stone."
• "Her coralsmiths went on to hollow out and buttress the reef into a huge, interconnected series of rooms and hallways that served simultaneously as fortress, palace, and diplomatic retreat."