1. a register or directory of socially prominent persons.
2. any register or directory, as of major companies or officials.
3. a blank book used in taking college examinations, usually with a blue cover.
4. a British parliamentary or other publication bound in a blue cover.
5. (caps.) Trademark.a reference manual listing the current market value of used cars by model and year of manufacture.
6. a similar manual listing the market value of other items, appliances, etc. Also,blue'book".