Source : Webster's Revised Unabridged Dictionary (1913)

Habituation \Ha*bit`u*a"tion\, n. [Cf. F. habituation.]
   The act of habituating, or accustoming; the state of being
   habituated.

Source : WordNet®

habituation
     n 1: being abnormally tolerant to and dependent on something that
          is psychologically or physically habit-forming
          (especially alcohol or narcotic drugs) [syn: {addiction},
           {dependence}, {dependency}]
     2: a general accommodation to unchanging environmental
        conditions