The practice of driving around residential areas (usually between the hours of 12-5 am), pulling up beside cars parked on the side of the street, and checking to see if they have been locked. If not, the car is stripped of anything inside. If so, the thieves move on. Cranking can also involve petty vandalism, leaving of handbrake off in a robbed car etc etc.
This practice originated in the eastern suburbs of Melbourne, Victoria, and has spread throughout the state.
Dude, check out this sweet GPS I got out cranking last night!