Source : Webster's Revised Unabridged Dictionary (1913)

Stet \Stet\, L., subj. 3d pers. sing. of stare to stand, remain.
   [See {Stand}.] (Print.)
   Let it stand; -- a word used by proof readers to signify that
   something once erased, or marked for omission, is to remain.

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.

Source : WordNet®

stet
     v 1: printing: cancel, as of a correction or deletion
     2: printing: direct that a matter marked for omission or
        correction is to be retained (used in the imperative)
     [also: {stetting}, {stetted}]