look up any word, like blumpkin:
 
2.
1. Incrase sharply

2. Inject illegal drugs

3. Raise a car to be able to do mechanical work
1. Jack up the oil prices

2. Jack up heroin four times a day

3. Jack up the car and change the tyre
by osmokozmo October 26, 2007
 
1.
Excessively short trousers resulting in the exposure of ankles, and in extreme cases, calves.
haha, look at them jack ups
by potusss January 23, 2007
 
3.
Derogative term for trousers worn too short (approx 1-3 inches above the shoe), often with white socks underneath making the jack-up more obvious.
Check that guy's jack-ups
My best trousers had shrunk, resulting in fairly serious jack-ups
by Nicky November 28, 2004
 
4.
commonly thought of as meaning trousers that are too short, 'jack-ups' are actually trousers that, surprise surprise, have been 'jacked' up. That means that the waistband has been pulled higher than necessary, possibly up to the naval (bellybutton) or chest.
person1: (indicating person2's trousers) ha, look, he's got jack-ups!

person2: actually, my trousers are just a bit short

person1's friend, person3: yeah thats what jack-ups are, you idiot

person2: commonly thought of as meaning trousers that are too short, 'jack-ups' are actually trousers that, surprise surprise, have been 'jacked' up. That means that the waistband has been pulled higher than necessary, possibly up to the naval (bellybutton) or chest.

person1 & person3: youre such a nerd
by A D August 13, 2007
 
5.
To jack-up is a gymrat term for working to improve a specific muscel or set of muscels, especially women who want to firm-up their butts.
She is doin something to jack-up that ass. I'll bet she spends an hour-a-day on the stairclimber."
by Jim Inman August 17, 2006