Simple past tense and past participle of flail.(verb)
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Use "flailed" in a sentence
"Before the Pict could straighten the red sword flailed down and clove him from shoulder to mid-breastbone where the blade stuck."
"Conan's sword flailed down, crunching through flesh and bone, and then the Cimmerian was dragging Balthus around the altar, past a huddled shaggy bulk on the floor, to a door at the back of the long hut."
"She smashed the head of the lich whose legs were severed at the knees, then did the same to one whose rusty sword flailed wildly even though its pelvis lay to one side of the upper body."