The Oxford English Dictionary
The premier historical dictionary of the English language. Entries for each sense of the word are illustrated with quotations from the full extent of written English.
The extensive Help section
includes links to the abbreviations used and bibliography of the Second Edition.
"The OED presents in alphabetical series the words that have formed the English vocabulary from the time of the earliest records down to the present day, with all the relevant facts concerning their form, sense-history, pronunciation, and etymology. It embraces not only the standard language of literature and conversation, whether current at the moment, or obsolete, or archaic, but also the main technical vocabulary, and a large measure of dialectical usage and slang. This online edition contains the complete A to Z sequence of the Second Edition, its three-volume Additions Series, and also draft material from the revision programme, which represents the latest progress towards the Third Edition." More about the OED