Dictionary.net

A common practice whereby an airline, hotel or other company accepts more reservations than it has seats or rooms available, on the presumption that a certain percentage of people will not show up. Airlines have a legal right to overbook, while hotels do not. A hotel must find a room for everyone who has a reservation and shows up on time. An airline may be required to offer compensation for people involuntarily bumped from a flight, depending on several factors, including how long they must wait for another flight.