The Collaborative International Dictionary of English v.0.48:

Rectification \Rec`ti*fi*ca"tion\ (r?k`t?*f?*k?1sh?n), n. [Cf.
   F. rectification.]
   1. The act or operation of rectifying; as, the rectification
      of an error; the rectification of spirits.
      [1913 Webster]

            After the rectification of his views, he was
            incapable of compromise with profounder shapes of
            error.                                --De Quincey.
      [1913 Webster]

   2. (Geom.) The determination of a straight line whose length
      is equal a portion of a curve.
      [1913 Webster]

   Rectification of a globe (Astron.), its adjustment
      preparatory to the solution of a proposed problem.
      [1913 Webster]

WordNet (r) 3.0 (2006):

rectification
    n 1: (chemistry) the process of refinement or purification of a
         substance by distillation
    2: the conversion of alternating current to direct current
    3: the act of offering an improvement to replace a mistake;
       setting right [syn: correction, rectification]
    4: determination of the length of a curve; finding a straight
       line equal in length to a given curve