Jacked up

Slang expressions often have regional differences, and they are regularly 'recycled'. Back in the 60s and 70s, young people would often put wider tires on the back of their car and raise the springs so the body would clear the bigger tires. The car was thus 'jacked up'.

I also heard "jack him/her up" used to refer to reminding someone about a commitment. "He must have forgotten to send the merchandise. I'm going to have to jack him up on that."

The other uses of Jacked Up mentioned are all good ones, meaning that something is supported- perhaps even elevated- but not very solidly...

I hear it a lot around where I live. I never heard it at all in the UK, but in the US, it's used a lot.

The other day in classes, we had just found out that our exam was going to last 2 hours and we couldn't leave right after we finished and a guy across the room said " Man, that's jacked up" as in... you know, an injustice or "that's not right!"

Jacked up = messed up; amped up. Also includes connotations of mugging.

Your face got jacked up. (Your face got messed up)
My car got jacked. (My car is stolen)
She was all jacked up on Red Bull and ran around the block four times.

It can also be somewhat of a more PG alternative to F---ed up at times.

In the south United States a truck can be jacked up (as someone else mentioned) which means the body has been raised and it has large tires.

Also something you own can be jacked which means stolen. Like, my computers been jacked.

It seems likely to me that the "stolen" connotation of "jacked" derives from the more established term "hijacked."

That is, if an airplane can be hijacked, an automobile can be "carjacked" ... which is then shortened to just "jacked."

Creating new words with old suffixes is a common practice in English, as evidenced by such examples as "dognapping" and "Climategate."