The Collaborative International Dictionary of English v.0.48:

Rectifiable \Rec"ti*fi`a*ble\ (r?k"t?*f?`?*b'l), a.
   1. Capable of being rectified; as, a rectifiable mistake.
      [1913 Webster]

   2. (Math.) Admitting, as a curve, of the construction of a
      straight line equal in length to any definite portion of
      the curve.
      [1913 Webster]

WordNet (r) 3.0 (2006):

rectifiable
    adj 1: capable of being repaired or rectified; "reparable damage
           to the car"; "rectifiable wrongs" [syn: reparable,
           rectifiable] [ant: irreparable]

Moby Thesaurus II by Grady Ward, 1.0:

20 Moby Thesaurus words for "rectifiable":
   ameliorable, amendable, correctable, corrigible, curable,
   emendable, fixable, improvable, medicable, mendable, reclaimable,
   recoverable, recyclable, redeemable, remediable, repairable,
   reparable, restorable, retrievable, reversible