Something accidentally lost or broken by leaving it atop of a vehicle before driving becoming the inadvertent flotsam and jetsam of modern land transportation. Common discargo items include a coffee mug on a car roof or a gas-cap left on a trunk. This may include unsecured items in the bed of a pick-up which on the highway scatter to the four winds, creating road hazards in the process.
Roger built his tool collection by riding his bicycle and picking up discargo.
Lily's take-out lunch became discargo on I-95.
One man's discargo, may become another man's treasure.