Source : Webster's Revised Unabridged Dictionary (1913)

Acclimation \Ac`cli*ma"tion\, n.
   The process of becoming, or the state of being, acclimated,
   or habituated to a new climate; acclimatization.

Source : WordNet®

acclimation
     n : adaptation to a new climate (a new temperature or altitude
         or environment) [syn: {acclimatization}, {acclimatisation}]