The Collaborative International Dictionary of English v.0.48:

Mackle \Mac"kle\, n. [See Macle.]
   Same as Macule.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Mackle \Mac"kle\, v. t. & i.
   To blur, or be blurred, in printing, as if there were a
   double impression.
   [1913 Webster]

WordNet (r) 3.0 (2006):

mackle
    n 1: a printed impression that is blurred or doubled