A sickness bag (also known as a sick sack, airsick bag, airsickness bag, emesis bag, sick bag, barf bag, vomit bag, disposal bag, waste bag, Doggie bag or motion sickness bag) is a small bag commonly provided to passengers on board airplanes and boats to collect and contain vomit in the event of motion sickness. Hovercraft-ferry operators and even train companies have also been known to furnish bags. People who know they are prone to motion sickness will sometimes bring their own bags.