When a man or woman puts both of there fists inside a butthole or vagina and moves in conjunction While one fist moves down the other goes up. Like a engine piston.
by Irishrover18 January 12, 2017

Slang referring to an aggressive, furious, rapid act of fellatio. The piston pump receives its name from the rapid head movement exhibited by the provider of the fellatio, which is said to resemble the action of a moving piston. This is also referred to as the jackhammer. The piston pump is much sought after in the world of fellatio and should be received with grace and humility.
by Boozy Barfly November 11, 2008

by lars fredricksen January 9, 2009

by TheHungryShoe September 28, 2020

“This town ain’t big enough for the both of us, you god darn piston neck”
“You fucking piston neck”
“What are ya? A fucking piston neck?!”
“Get off my land you piston neck”
Or if you are a women
“Get your willy out of my face you piston neck”
“Get off my behind, you piston neck lookin retard”
Honourable mentions
Piston Neck Pete
Piston Neck Willy
“You fucking piston neck”
“What are ya? A fucking piston neck?!”
“Get off my land you piston neck”
Or if you are a women
“Get your willy out of my face you piston neck”
“Get off my behind, you piston neck lookin retard”
Honourable mentions
Piston Neck Pete
Piston Neck Willy
by TheHungryShoe September 28, 2020

When your going anal with a bitch and she shits while your dicks in her ass forcing it back out like a piston.
by Donkeykong2128 May 31, 2015

Yet another slang term for penis. It is meant to be humorous and not as offensive as some other slang terms.
Fred : "Dude, I thought Darcy was leaving you."
John : "What can I say? She can't get enough of my butter piston."
John : "What can I say? She can't get enough of my butter piston."
by Huge Assman November 2, 2017
