2.
flail n. & v.
—n. a threshing-tool consisting of a wooden staff with a short heavy stick swinging from it.
—v.
1 tr. beat or strike with or as if with a flail.
2 intr. wave or swing wildly or erratically (went into the fight with arms flailing).
Etymology: OE prob. f. L FLAGELLUM
Useful english dictionary. 2012.