This page contains dictionary definitions of ‘vegan’ available for free on the internet. Only unique definitions from their original source are included. Medical, etymology, and slang dictionaries are excluded. Related pages look at definitions offered by news media and animal advocates. My use of the term is unlike those here, but it's consistent with the history of veganism.
Dietary Behaviors Only
Variety of Vegetarian
"A strict vegetarian; someone who eats no animal or dairy products at all."
Oxford English Dictionary [pdf]
"A person who on principle abstains from all food of animal origin; a strict vegetarian."
Random House Dictionary
"A vegetarian who omits all animal products from the diet."
The Collaborative International Dictionary of English v.0.48
"A vegetarian who does not eat any animal products, not even fish, eggs, or milk."
Webster's New World College Dictionary
"A vegetarian who eats no animal products."
Babylon English Dictionary
"Vegetarian who does not eat any animal products."
Ultralingua Online Dictionary
"A strict vegetarian; someone who eats no animal or dairy products at all"
Vegetarian Not Mentioned
Longman Dictionary of Contemporary English
"Someone who does not eat any animal products at all, such as meat, fish, eggs, cheese, or milk."
Encarta World English Dictionary
"Somebody who does not eat meat, fish, dairy products, or eggs."
Macmillan English Dictionary
"Someone who chooses not to eat anything derived (=made) from animals or fish, including eggs, milk, and cheese."
"One who abstains completely from the consumption of animal products, including meat, dairy products, and eggs."
Beyond Dietary Behaviors
American Heritage Dictionary of the English Language
"A vegetarian who eats plant products only, especially one who uses no products derived from animals, as fur or leather."
Merriam-Webster’s Online Dictionary
"A strict vegetarian who consumes no animal food or dairy products ; also : one who abstains from using animal products (as leather)."
Chambers 21st Century Dictionary
"Someone who does not eat meat, fish, dairy products or any foods containing animal fats or extracts, such as eggs, cheese and honey, often also avoiding using wool, leather and other animal-based substances."
Oxford Advanced Learner's Dictionary
"A person who does not eat any animal products such as meat, milk or eggs. Some vegans do not use animal products such as silk or leather."
WordWeb Online Dictionary
A strict vegetarian; someone who eats no animal or dairy products; may also avoid using animal products (e.g. leather)
Cambridge Advanced Learner's Dictionary
"A person who does not eat or use any animal products, such as meat, fish, eggs, cheese or leather."
"A person who does not consume, use or eat any animal products."
Oxford Dictionaries (US English)
"A person who does not eat or use animal products."
Collins English Dictionary
"A person who refrains from using any animal product whatever for food, clothing, or any other purpose"
"A person who will not eat or use any type of animal product."