›a list of orders for products or services that a business keeps, often used to measure how successful and profitable it is at a particular time: The group's order book has continued to expand as a result of buoyant trading in Asia.The aerospace engineering company has a record order book of £16.7bn.a solid/strong/growing order booka $70,000/$350m/$2.3bn order bookan order book grows/stands atTheir order book currently stands at £219 million, up 79% on the same period three years ago.