noun
a thin, flat piece of something that can be moved to cover or close an opening
verb
to move up and down or from side to side with a quick, light, slapping sound
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The bird's wings began to flap rapidly as it took off into the sky.
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I saw the dog flap its ears when it heard a loud noise.
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She started to flap when she realized she was running late.
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His hands began to flap in excitement as he told the story.