The Collaborative International Dictionary of English v.0.48:

Stet \Stet\, v. t. [imp. & p. p. Stetted; p. pr. & vb. n.
   Stetting.] (Print.)
   To cause or direct to remain after having been marked for
   omission; to mark with the word stet, or with a series of
   dots below or beside the matter; as, the proof reader stetted
   a deled footnote.
   [1913 Webster]