1.To use ones head to engineer a solution to an existing problem,
2.to illegally configure something for ones advantace
both usually done by irish or scotts-men as they just seem to be good at that stuff
1.Sean- "Hey Stewie, how are you mounting your speakers on the wall?"
Stewie- "I jimmied-up some shelves from some scrap paper and used an old shoe string to support it."
2. "Wow those fuckers jimmied-up some cable over there, meanwhile use douches are payin hard"