Source : Webster's Revised Unabridged Dictionary (1913)

Digression \Di*gres"sion\, n. [L. digressio: cf. F. digression.]
   1. The act of digressing or deviating, esp. from the main
      subject of a discourse; hence, a part of a discourse
      deviating from its main design or subject.

            The digressions I can not excuse otherwise, than by
            the confidence that no man will read them. --Sir W.
                                                  Temple.

   2. A turning aside from the right path; transgression;
      offense. [R.]

            Then my digression is so vile, so base, That it will
            live engraven in my face.             --Shak.

   3. (Anat.) The elongation, or angular distance from the sun;
      -- said chiefly of the inferior planets. [R.]

Source : WordNet®

digression
     n 1: a message that departs from the main subject [syn: {aside},
          {excursus}, {divagation}, {parenthesis}]
     2: a turning aside (of your course or attention or concern); "a
        diversion from the main highway"; "a digression into
        irrelevant details"; "a deflection from his goal" [syn: {diversion},
         {deviation}, {deflection}, {deflexion}, {divagation}]
     3: wandering from the main path of a journey [syn: {excursion}]