Other forms: boarding passes
A boarding pass is a document that allows you to board a ship or plane. Without a boarding pass, you can't get aboard.
If you've ever flown on a plane, you're probably familiar with boarding passes. A boarding pass is something you either print at home or get at the airport. It's a ticket that specifically allows you entrance to the airplane (or if you're traveling by sea, a boat). If you lose your boarding pass, you won't be allowed to board. Boarding passes allow the airline to make sure the people on the plane all bought tickets and belong there.