One way to use the word "flap" is as a verb. Animals that fly, especially birds, flap their wings in order to move through the air.
When the word "flap" is used as a noun, it refers to that part of a box or an envelope that folds and seals whatever is inside.
There are some other ways to use the word "flap."
A flag flaps in the wind. This flag is flapping in the wind.
Pancakes are sometimes referred to as flapjacks. He’s sitting behind a stack of flapjacks.
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August 8, 2019