Both Uses

writhe
in
The Return of the King
(Auto-generated)

there lay his weapon, but the blade was smoking like a dry branch that has been thrust in a fire; and as he watched it, it writhed and withered and was consumed.†
Chpt 5.6 *

writhed = moved in a twisting or contorted motion
In the glens of the Morgai on the other side of the valley low scrubby trees lurked and clung, coarse grey grass-tussocks fought with the stones, and withered mosses crawled on them; and everywhere great writhing, tangled brambles sprawled.†
Chpt 6.2

writhing = moving in a twisting or contorted motion

Definitions:

(1) (writhe)
to move in a twisting or contorted motion -- often of a person when struggling or in pain
(2) (meaning too rare to warrant focus)