Ron bellowed, and he started to writhe and struggle against the ropes tying them together, so that Harry staggered.
It jabbed at a place near the roots, and at once, the writhing tree became still.
He writhed through the air like a drowning man, thrashing and howling in pain, and then, with a crunch and a shattering of glass, he smashed into the front of a bookcase and crumpled, insensible, to the floor.
He barely made it: Bolting the door behind him with trembling hands, he grasped his pounding head and fell to the floor, then in an explosion of agony, he felt the rage that did not belong to him possess his soul, saw a long room lit only by firelight, and the giant blond Death Eater on the floor, screaming and writhing, and a slighter figure standing over him, wand outstretched, while Harry spoke in a high, cold, merciless voice.
Harry felt as though he turned into slow motion: he saw McGonagall, Kingsley and Slughorn blasted backward, flailing and writhing through the air, as Voldemort’s fury at the fall of his last, best lieu-tenant exploded with the force of a bomb, Voldemort raised his wand and directed it at Molly Weasley.
And Harry saw the white hand raise its wand and felt Voldemort’s surge of vicious anger, saw the frail old main on the floor writhe in agony — "Harry?
What?" he bellowed, writhing in his attempts to free himself from Ron’s grip.
There are no more uses of "writhe" in the book.
Show samples from other sources
The patient writhed in pain.
She writhed on the sidewalk begging that someone call an ambulance.