The Collaborative International Dictionary of English v.0.48:

Retrogradation \Re`tro*gra*da"tion\, n. [F. r['e]trogradation or
   L. retrogradatio. See Retrograde.]
   1. The act of retrograding, or moving backward.
      [1913 Webster]

   2. The state of being retrograde; decline.
      [1913 Webster]