A very hyper dog that can also be your best friend in the world!
Boy, that jack russell sure does love humpin thangs! I had to rip him off the neighbors cat eairlier!
by Jam_the_surfer June 25, 2007
Jack russell is a crazy small breed of the Gray wolf, if you hit him, he will hit you back.
In the picture above (or bellow, i dunno) you can see a dead jack russell, for a living jack russell never rest.
Human 1: He's running like a jack russell.
Human 2: See? he got tired, a Jack russell will never get tired.

Or:

Labrador: the fuck, why are you running in cyrcles?
Jack russell: I love you.
by Homo-Sapiens February 17, 2016
the most hyper annoying crazy dogs in the world. well sometimes lol they are very fast . sometimes they can be the funnyest dogs ever . but also ur best bud :)
simon, harley, jessey, pepper, jack russell
by mysterious lover;) March 15, 2010
To grab your girlfriends anus hair between your teeth and shake your head vigorously. Just like a Jack Russell wrestling with a piece of rope.

Similiar to motorboating but rectal and hairy.
I was Jack Russelling a girl I met in town all night and now my neck hurts.
by Daddybot April 29, 2012
The act of vigorously shoving your dick into someone's bum,
"I'd give her The Jack Russell, lad"
or
"I'd be up the back of her like The Jack Russell"
or
"I heard John give Amie The Jack Russell, last Friday"
by ZPL400 January 23, 2015
To grab your partners anal hair between your teeth and shake your head vigorously, much like a Jack Russel wrestling with a piece of rope.
"Bro, see that girl accross the bar, I am so gonna be Jack Russelling her later"
by Daddybot July 9, 2012
The act of sex where the speed and sexual position imitate that of Jack Russell humping a teddy bear, football or leg!
He was "Jack Russelling" her last night

or

I going to be "Jacking Russelling" that later
by Bananabridge December 10, 2009