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]

WordNet (r) 3.0 (2006):

vegan
    n 1: a strict vegetarian; someone who eats no animal or dairy
         products at all