writhe

Short definition from Wiktionary

Verb

1. 1
   To twist, wring (something).
2. 2
   To contort (a part of the body).
3. 3
   To twist bodily; to contort one's self; to be distorted.
4. 4
   To extort.

Noun

1. 1
   A contortion.
2. 2
   The number of negative crossings subtracted from the number of positive crossings in a knot