This is simply the act of using your hand as a kleenex during awkward times where any kind of tissue/toilet paper/paper towel/gum wrapper is nowhere to be found. The handsnot is then wiped on something else, usually one's sock.
Man, I had a cold last weekend at Bertha's parents' cottage and pulled a handnex right in front of her grandmother. She handed me a used maxi to wipe it on, what a saint.
Handnesia is when you owe a guy money, but you give him a handjobinstead of paying him, so he "forgets" you haven't paid him
Didn't Kill owe you $40?
Yeah, but she gave me a handjobthe other night and now I don't want to ask her for it because she'll think I'm cheap.
She got you with the old handnesia trick