Jetsam
Anything which is voluntarily cast overboard from a vessel in time of distress. See "Jettison" and "Flotsam."
Jettison
The deliberate throwing overboard of cargo, or of part of the vessel's superstructure, equipment or stores, in the event of an emergency. Cargo or equipment might be jettisoned to lighten a vessel to relieve it from a strand, to stabilize it during a storm, or to get rid of flammables or explosives during a fire. (Washing overboard is the accidental loss of equipment or cargo overboard due to the action of the elements.)
Flotsam
Floating wreckage of a vessel or its cargo. See "Jetsam" and "Lagan."
Lagan (Ligan)
A heavy article thrown overboard with a buoy to mark where it is located for recovery at a later time; e.g. crab pots.
General Average (GA)
An ancient principle of equity, recognized by maritime nations, pre-dating the concept of insurance and still valid today, in which all parties involved in a sea adventure (vessel, cargo, and freight) proportionately share losses resulting from a voluntary and successful effort to save the entire venture from an imminent peril. There are two types of General Average acts:
1. Voluntary Sacrifice of a part of the vessel or a part of the cargo, e.g. jettison of property to stabilize the vessel during heavy weather.
2. Extraordinary Expense necessarily incurred for the joint benefit of vessel and cargo, e.g. towing charges incurred to assist a disabled vessel to a port of refuge.
http://www.amusf.com/Definitions_G.htm
Another legal explanation of General Average:
https://en.wikipedia.org/wiki/General_average
[One link was updated on August 21, 2016 by shuehorn]
