From the Oxford English Dictionary, 2d ed.

vegan

[f. veg(etable n. + -an.]

1. A person who on principle abstains from all food of animal origin; a strict vegetarian.

1944 D. Watson in Vegan News Nov. 2 'Vegetarian' and 'Fruitarian' are already associated with societies that allow the 'fruits' of cows and fowls, therefore..we must make a new and appropriate word... I have used the title 'The Vegan News'. Should we adopt this, our diet will soon become known as the vegan diet, and we should aspire to the rank of vegans. 1945 Ibid. Feb. 3 Two members have asked how 'Vegan' is pronounced. Veegan, not Veejan. 1955 Irish Press 29 Nov. 618 A true-blue Vegan, I'm assured,..will even exclude from his or her diet, milk and..honey. 1965 New Scientist 20 May 526/3 Vitamin B12.. is found almost exclusively in animal foods, so that strict vegetarians (like vegans) may go short unless they take special precautions to ensure a supply. 1977 J. F. Fixx Compl. Bk. Running xiv. 170 There are..three kinds of vegetarians: the 100 percent vegetarian, sometimes called a vegan; the lacto-vegetarian..; and the lacto-ovo-vegetarian. 1979 J. I. M. Stewart Our England 177 Robin had discovered the duty of being a vegetarian. Indeed, he had become a vegan, and that seemed to mean that he could eat virtually nothing at all. 1985 Times 1 Feb. 12/2 'Beanmilk: milk that's never even seen a cow' is to vegans, who deplore exploitation of animals and eat nothing derived from them, a highly desirable commodity.

2. attrib. or as adj.

1944 [see sense 1 above]. 1945 Vegetarian Messenger XLII. 163 Following the articles and correspondence regarding the use of dairy products..in The Vegetarian Messenger last year, a number of our members who do not use animal products of any kind formed themselves into a group which has since adopted the title of 'The Vegan Society'. 1951 News Chron. 13 Dec. 3 A true vegetarian or vegan diet may not be nutritionally adequate, said Dr. Hill. 1973 Listener 8 Feb. 178/1 The good ecological life; no car, vegan cooking, and a mangle technology in a tumbledown cottage. 1978 Peace News 25 Aug. 18/3 A group of people from a 1750 acre vegan farming community in Tennessee..are coming to visit Britain in late September or early October. 1984 Listener 9 Aug. 17/2 The facts that CIWF is able to marshal must drive many who read its literature to a vegan diet.

Hence veganism, the beliefs or practice of vegans; abstention from all food of animal origin.

1944 Vegan News May 1 Veganism is the practice of living on fruits, nuts, vegetables, grains, and other wholesome non-animal products. 1972 New Scientist 4 May 297/2 Universal vegetarianism would..tend to disrupt organic farming and the organic cycle—soil, plant, animal, man. It would also, if logically carried on as in Veganism, abolish milk and eggs. 1977 S. R. L. Clark Moral Status of Animals ix. 185 Veganism is a better project than lacto-vegetarianism, though we may in the end be able to take some milk from our kin without injustice.