The action of the verb to flex; a bending of something, a tightening of the muscles.(noun)
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Use "flexing" in a sentence
"That's what I call flexing your imagination muscle!"
"That kind of flexing comes from the bespectacled “King Wild Boar” himself, Karl Rove."
"A good idea when they were originally conceived, but, in flexing their muscles and demanding more of everything, have priced themselves and the products they represent, out of business."