Oxford English Dictionary

The Oxford English Dictionary, the OED, is considered the authority on the evolution of the English language. It is published by Oxford University Press.

Overview
The dictionary presents the meaning, history, and pronunciation of over half a million words and traces their use through 2.5 million quotations from a wide range of international English language sources, including North America, South Africa, Australia, New Zealand and the Caribbean.

The OED is a historical dictionary, and its entry structure is therefore different from that of dictionaries of current English, which only cover present-day senses, and in which the most common meanings are described first.

The Second Edition of the OED is available as a 20-volume print edition, with 21,730 pages, on CD-ROM, and online.

Snippets

 * Longest entry in Dictionary: the verb ‘set’ with over 430 senses