WordNet (r) 3.0 (2006):

synchronicity
    n 1: the relation that exists when things occur at the same
         time; "the drug produces an increased synchrony of the
         brain waves" [syn: synchronism, synchrony,
         synchronicity, synchroneity, synchronization,
         synchronisation, synchronizing] [ant: asynchronism,
         asynchrony, desynchronisation, desynchronization,
         desynchronizing]