Triple fisting is something you have to do when you are already holding something in each of your hands and someone else hands you something.
Here can you hold my beer for me? Sure. Oh can you hold mine to? you'll have to triple fist it.
"I'm triple fisting Armand"
Inserting three different fists in to the anus or vagina, wherever there happens to be more room. You can get the third fist from a friend. (owwie)
British man has three beers in his hand:
Hot girl named Kirstin: oh, you're triple fisting it, eh?
British Man: Excuse me!?!?!?!?
Hot girl named Kirstin: you have three beers in your hand.
British Man: In my country that means to fist...using three fists.
Consuming three beers at one time, generally by having one beer in each hand, and another one in your front shirt pocket with a straw.
Jeff was triple fisting with a Bud, an MDG and a Coors