Goods which sink when cast into the sea, and remain under water; -- distinguished from flotsam, goods which float, and ligan (or lagan), goods which are sunk attached to a buoy.  [1913 Webster]

 The act of throwing objects from a ship to lighten the load; jettison{1}. See Jettison, 1.  [1913 Webster]

 Anything thrown overboard from a ship, whether floating or not.  [PJC]

 Objects scattered about in a disorderly manner; as, he couldn't find his sneakers among the jetsam in his room.  [PJC]