Jetsam is cargo or equipment that sailors deliberately throw overboard from a ship, usually to lighten the vessel during an emergency. When a ship is sinking or caught in a dangerous storm, the crew might toss heavy items into the sea to help the ship stay afloat. Those items washing up on shore or floating in the water are jetsam.

Jetsam differs from flotsam, which is wreckage that floats away when a ship sinks accidentally. If you spot wooden crates or barrels on a beach after a storm, they might be jetsam from a ship that survived by throwing them overboard.

You'll often hear the phrase flotsam and jetsam used together to describe scattered debris or odds and ends, like when someone says a garage is filled with “the flotsam and jetsam of twenty years.” In this everyday usage, it means random junk or discarded items.