The Collaborative International Dictionary of English v.0.48:

Adaptation \Ad`ap*ta"tion\, n. [Cf. F. adaptation, LL.
   adaptatio.]
   1. The act or process of adapting, or fitting; or the state
      of being adapted or fitted; fitness. "Adaptation of the
      means to the end." --Erskine.
      [1913 Webster]

   2. The result of adapting; an adapted form.
      [1913 Webster]

WordNet (r) 3.0 (2006):

adaptation
    n 1: a written work (as a novel) that has been recast in a new
         form; "the play is an adaptation of a short novel" [syn:
         adaptation, version]
    2: the process of adapting to something (such as environmental
       conditions) [syn: adaptation, adaption, adjustment]
    3: (physiology) the responsive adjustment of a sense organ (as
       the eye) to varying conditions (as of light)