Likely by illegal or dubious means. Said of the way something has been gotten. Primarily heard in US, Australia. A: "Jake's been peddling a bunch of flat screens for a great price." A: "He probably got them off the back of a truck. I wouldn't go for them, if I were you." Danny says he has several laptops and smartphones he wants to sell for cheap—sounds like they fell off the back of a truck to me.