Fisting

Fisting

to insert the full hand into the vagina or anus for masturbation purposes, often curling the hand up once inside into a fist for maxium size.

Fisting is one of the sex acts that some consider obscene, as it involves a level of insertion that they are not comfortable with. Many sites that do fisting use girls or guys with incredibly small hands, but some really do go all the way. Many of them also do full hand insertions but do not curl the hand up.