c.f.
handballing.
Fisting is the art of inserting the hand (past the knuckles, to the wrist) into the vagina, the anus, or some other orifice of the body. It is generally considered to be a BDSM activity, in that it pushes the limits of the body beyond what they're normally expected to handle.
(In the gay BDSM community, fisting is called 'handballing', and is part of a larger set of activities called 'assplay'.)
A couple of notes about fisting:
- The practice is performed, in the course of their work, by veterinarians, especially when midwifing the birth of a calf, foal, or other large animal.
- The earliest known record of someone requesting to be fisted was Jesus. (When Thomas doubted his authenticity as his Lord, Jesus asked him to put his hand within the hole that the Roman's spear made.)