Here is another definition
http://www.slangcity.com/ask_ac_archive/balling%20_the_%20jack.htm

Dear Slang City:

1. What does "balling the jack" mean and what is its origin? I hope it's not gross......


To answer your first question, "balling the jack" has several meanings. None of them are used much these days, but maybe the expression may become more popular because of the recent novel, Balling the Jack, by Frank Baldwin. It's being made into a movie, starring Ben Affleck as a gambler, and the expression means "risking everything on one attempt" - in this case, he bets $40,000 on a dart game.

However, that's not the original meaning of the word. It was the name of a popular dance in 1913, which goes like this:

"First you put your two knees close up tight
Then you sway them to the left, then you sway them to the right
Step around the floor kind of nice and light
Then you twist around and twist around with all your might,
Stretch your loving arms straight out into space,
Then you do the Eagle Rock with style and grace.
Swing your foot way 'round then bring it back.
Now that's what I call Ballin' the Jack."

Later, the meaning was expanded from just "dancing" to "having a great time". Around the same time the song came out, the expression was used by railroad workers to mean "going at full speed." It's not clear whether the dance or railroad reference came first. And (if that's not enough) it's also been used to describe operating a jackhammer.

So it wasn't anything gross (disgusting), though you can find later uses of the expression where it has a sexual meaning, similar to "balling" (having sex). For example, in the 1940s, blues artist Big Bill Broonzy sang:

My baby's coming home.
I hope that she won't fail because I feel so good, I feel so good.
You know I feel so good, feel like balling the jack.

Well, he could be talking about dancing… but maybe not.

6.15.04
I recently got an interesting email on this topic from a reader:

"To "ball" a "jack" refers possibly to the action of risking a shot in "Boules", or Bocce or its sister game Petanque. The jack in either case is the smaller ball for which the goal of the game is to either throw your team's ball closest to it, or to knock away your opponent's ball. To hit the target ball to another location, or to "ball the jack", is to alter the focus of the gameplay. To do so requires great accuracy, and assuming the game is scored for money instead of points (it is a drinking game, and takes skill and a bit of luck as well), takes risk as well, for in double or triple team play, you only get one shot (one ball per player). So to "ball the jack" is to risk a miss, and a wasted shot, at something that is really important to you."

Thanks to Nasmichael for this info!

11.14.05
More information on the railway origins from Steve, who says

Believe it or not I was looking for "balling the jack" after listening to my new Hobart Smith record. He sings the Broonzy tune you quoted and there's no doubt what he meant there :-). But I think the phrase has it's origins in how men worked on the railway. Hobart does another song with the lines "Balling the jack, lining track / You can't shovel no more" and the liner notes say it comes from railroad section gangs in the early 1870's. Now if you look up railway know-how on http://madisonrails.railfan.net/lewman10.html you will see that to fix a crooked rail you had one person sit on the track and site along it to see where it needed to be straightened (lining the track), then two men would put jacks at an angle against the inside ball of the rail and lever it until it was straight. Then you had to shovel ballast back in under the ties and tamp it down. The ball of the rail is the curved part going up to the flattened surface on top of the rail. The jack had a groove across the top that fit against the ball so it wouldn't slip off.