Source : Webster's Revised Unabridged Dictionary (1913)

Regress \Re"gress\ (r?"gr?s), n. [L. regressus, fr. regredi,
   regressus. See {Regrede}.]
   1. The act of passing back; passage back; return;
      retrogression. ``The progress or regress of man''. --F.
      Harrison.

   2. The power or liberty of passing back. --Shak.

Regress \Re*gress"\ (r?*gr?s"), v. i. [imp. & p. p. {Regressed}
   (-gr?st"); p. pr. & vb. n. {Regressing}.]
   To go back; to return to a former place or state. --Sir T.
   Browne.

Source : WordNet®

regress
     n 1: the reasoning involved when you assume the conclusion is
          true and reason backward to the evidence [syn: {reasoning
          backward}]
     2: returning to a former state [syn: {regression}, {reversion},
         {retrogression}, {retroversion}]
     v 1: go back to a statistical means
     2: go back to a previous state; "We reverted to the old rules"
        [syn: {revert}, {return}, {retrovert}, {turn back}]
     3: get worse; fall back to a previous or worse condition [syn:
        {retrograde}, {retrogress}] [ant: {progress}]
     4: go back to bad behavior; "Those who recidivate are often
        minor criminals" [syn: {relapse}, {lapse}, {recidivate}, {retrogress},
         {fall back}]