(third-person singular simple present flails, present participle flailing, simple past and past participle flailed)
- To beat using a flail or similar implement.
- To wave or swing vigorously
- To thresh.
- (intransitive) To move like a flail.
- He was flailing wildly, but didn't land a blow.
From Middle English flaile, flayle, from earlier Middle English fleil, fleyl, fleȝȝl, flegl, from Old English fligel, *flegel (“flail”), from Proto-Germanic *flagilaz (“flail, whip”), of uncertain origin. Cognate with Scots flail (“a thresher's flail”), West Frisian fleil, flaaiel (“flail”), Dutch vlegel (“flail”), Low German vlegel (“flail”), German Flegel (“flail”). Possibly a native Germanic form from Proto-Germanic *flag-, *flah- (“to whip, beat”), from Proto-Indo-European *plak-, *plāk- ("to beat, hit, strike; weep"; compare Lithuanian plàkti (“to whip, lash, flog”), Ancient Greek πληγνύναι (plēgnýnai, “strike, hit, encounter”), Latin plangō (“lament", i.e. "beat one's breast”)) + Proto-Germanic *-ilaz (instrumental suffix); or a borrowing of Latin flagellum, diminutive of flagrum (“scourge, whip”), from Proto-Indo-European *bʰlag-, *bʰlaǵ- ("to beat"; compare Old Norse blekkja (“to beat, mistreat”)). Compare also Old French flael (“flail”), Italian flagello (“scourge, whip, plague”).