- (uncountable) Collectively, items that have been or are about to be ejected from a boat or balloon.
- (countable) The action of jettisoning items.
- To let go or get rid of as being useless or defective; discard.
- To eject from a boat, submarine, aircraft, spaceship or hot-air balloon, so as to lighten the load.
"The jettisoning of fuel tanks."
"The ballooners had to jettison all of their sand bags to make it over the final hill."