Overbooked means sold to more passengers than there are seats. An overbooked flight, overbooked hotel, overbooked by four.
Airlines do it deliberately because a predictable share of passengers never turn up, and the practice is legal and compensated when it goes wrong. Compensation for being denied boarding is set by regulation in Europe. Note that the over- means excessively, as in overcooked.
1adjectiveoverbookedSold to more passengers than there are seats.
“The flight was overbooked, so the airline offered us money to take a later one.”
overbooked is a state of oversale.
overbook comes from over- + book.
Etymology from Wiktionary, CC BY-SA