Wiktionary
vb. (context intransitive English) To wave one's arms (or upper body) about violently, rather like a flail.
Usage examples of "flail about".
His arms and legs seemed to flail about more like long blades of grass than go as he wanted them to.
Beside her, the snakes of her whip stirred, but they didn't flail about as Pharaun feared they would.
He would take a hop at one of the lower branches, flail about with his legs, then drop groundward and crouch for a moment peering around the trunk toward the river.
With all the contradictory impulses in the loop, nothing was accomplished, and the two could only flail about in chaos, their spastic motions cycling through a Wrestle-mania strange attractor.
The troll began to flail about wildly, his battle now waged against gravity, not me.
With all the contradictory impulses in the loop, nothing was accomplished, and the two could only flail about in chaos, their spastic motions cycling through a Wrestle-mania strange artractor.
The impact seemed to revive it somewhat, and it began to flail about in a wild panic.
He began to scream and flail about in his gold-filled coffin, flinging coins in every direction.
I took my other han to try to cover her up, but she start makin noises an flail about wild-like, an me, I'm tryin to hole onto her so's she don't fall down again or come undone an there's people around us lookin back tryin to see what all the commotion is about.