The Collaborative International Dictionary of English v.0.48:

aneurin \aneurin\ n.
   Same as thiamin; a B vitamin (vitamin B1) that prevents
   beriberi. [Also spelled aneurine.]

   Syn: vitamin B1, thiamin, antiberiberi factor
        [WordNet 1.5] aneurysmal
        aneurismatic

WordNet (r) 3.0 (2006):

aneurin
    n 1: a B vitamin that prevents beriberi; maintains appetite and
         growth [syn: vitamin B1, thiamine, thiamin,
         aneurin, antiberiberi factor]