a book or set of books containing articles on various topics, usually in alphabetical arrangement, covering all branches of knowledge or, less commonly, all aspects of one subject.

( initial capital letter ) the French work edited by Diderot and D'Alembert, published in the 18th century, distinguished by its representation of the views of the Enlightenment.

noun

reference book , book of knowledge , almanac , compilation , concordance , cyclopedia