WordNet (r) 3.0 (2006):

Ypres
    n 1: battle in World War I (1917); an Allied offensive which
         eventually failed because tanks bogged down in the
         waterlogged soil of Flanders; Germans introduced mustard
         gas which interfered with the Allied artillery [syn:
         Ypres, battle of Ypres, third battle of Ypres]
    2: battle in World War I (1915); Germans wanted to try chlorine
       (a toxic yellow gas) as a weapon and succeeded in taking
       considerable territory from the Allied salient [syn: Ypres,
       battle of Ypres, second battle of Ypres]
    3: battle in World War I (1914); heavy but indecisive fighting
       as the Allies and the Germans both tried to break through the
       lines of the others [syn: Ypres, battle of Ypres, first
       battle of Ypres]