When a mechanic has no ability to troubleshoot a problem. Instead shoots the "parts cannon" at the problem. He ends up replacing every component in the system in hopes of fixing whatever was causing the problem. A complete waste of material and labor.
Customer: My breaks are squeaking.
Dumb Mechanic: You need new brake calipers, pads, rotors and wheel bearings. FIRE THE PARTS CANNON!
Nickname given to bales of marijuana thrown overboard or out of airplanes. Origin is reportedly from members of the US Coast Guard in the area of Southern Florida.