double-book Syllabification: (dou·ble-book)Translate double-book | into Italian | into Spanish Definition of double-book verb [with object] (usually be double-booked) reserve (something, especially a seat or a hotel room) for two different customers or parties at the same time:the hotel was double-booked book (someone) into a seat or room that is already reserved for another. double-book in other Oxford dictionaries Definition of double-book in the British & World English dictionary