From The Collaborative International Dictionary of English v.0.48 :
vegan \ve"gan\ (v[=e]"g[u^]n or v[=e]j"[u^]n), n.
A vegetarian who does not eat any animal products, not even
fish, eggs, or milk.
[PJC]
From WordNet (r) 2.0 :
vegan
n : a strict vegetarian; someone who eats no animal or dairy
products at all