On the OED
I want to clarify the use of the OED, and I'll simply tell you what they say:
The Oxford English Dictionary is the accepted authority on the evolution of the English language over the last millennium. It is an unsurpassed guide to the meaning, history, and pronunciation of over half a million words, both present and past. It traces the usage of words through 2.5 million quotations from a wide range of international English language sources, from classic literature and specialist periodicals to film scripts and cookery books.
The OED covers words from across the English-speaking world, from North America to South Africa, from Australia and New Zealand to the Caribbean. It also offers the best in etymological analysis and in listing of variant spellings, and it shows pronunciation using the International Phonetic Alphabet.
As the OED is a historical dictionary, its entry structure is very different from that of a dictionary of current English, in which only present-day senses are covered, and in which the most common meanings or senses are described first. For each word in the OED, the various groupings of senses are dealt with in chronological order according to the quotation evidence, i.e. the senses with the earliest quotations appear first, and the senses which have developed more recently appear further down the entry. In a complex entry with many strands, the development over time can be seen in a structure with several 'branches'.
The function is to present the evolution of words–to tell you what they have meant, and not necessarily what they mean or how they are used in 2009 (there's lag time). Common usage is on our side here, as the more we define and use vegan (or whatever word) to mean X–in (for now, traditionally published) print–the greater the odds of vegan showing up as meaning X in the OED some day.
For greater appreciation of the OED and what it took to compile the first one, I highly recommend Simon Winchester's The Professor and the Madman.
The Professor and the Madman is a terrific read, but don't forget Winchester's companion volume, The Meaning of Everything, which tells the larger picture of the making of the OED. It took seventy years of painstaking work to assemble the first edition, whose incredibly ambitious goal was to chronicle the various meanings of every word ever used in the language, past and present. Only after the massive dictionary was published was it discovered that one word had been accidentally omitted, because the slips of paper for it had fallen down out of sight behind some books. Thanks to Winchester's story, that word is burned into my memory. (And, no, I'm not telling.)