WordNet (r) 3.0 (2006):

overcompensation
    n 1: (psychiatry) an attempt to overcome a real or imagined
         defect or unwanted trait by overly exaggerating its
         opposite
    2: excessive compensation

Moby Thesaurus II by Grady Ward, 1.0:

32 Moby Thesaurus words for "overcompensation":
   alienation, autism, autistic thinking, avoidance mechanism,
   blame-shifting, compensation, decompensation, defense mechanism,
   dereism, dereistic thinking, displacement, dissociation,
   emotional insulation, escape, escape into fantasy,
   escape mechanism, escapism, fantasizing, fantasy, flight,
   isolation, negativism, projection, psychotaxis, rationalization,
   resistance, sociological adjustive reactions, sublimation,
   substitution, wish-fulfillment fantasy, wishful thinking,
   withdrawal