The Collaborative International Dictionary of English v.0.48:

Acclimatize \Ac*cli"ma*tize\ ([a^]k`kl[imac]"m[.a]*t[imac]z), v.
   t. [imp. & p. p. Acclimatized
   ([a^]k`kl[imac]"m[.a]*t[imac]zd); p. pr. & vb. n.
   Acclimatizing ([a^]k`kl[imac]"m[.a]*t[imac]`z[i^]ng).]
   To inure or habituate to a climate different from that which
   is natural; to adapt to the peculiarities of a foreign or
   strange climate; said of man, the inferior animals, or
   plants.
   [1913 Webster]

WordNet (r) 3.0 (2006):

acclimatize
    v 1: get used to a certain climate; "They never acclimatized in
         Egypt" [syn: acclimatize, acclimatise, acclimate]