Source : Webster's Revised Unabridged Dictionary (1913)

Prolusion \Pro*lu"sion\, n. [L. prolusio, fr. proludere to
   prelude; pro before + ludere to play: cf. F. prolusion, It.
   prolusione.]
   A trial before the principal performance; a prelude; hence,
   an introductory essay or exercise. ``Domestic prolusions.''
   --Thackeray.

         Her presence was in some measure a restraint on the
         worthy divine, whose prolusion lasted.   --Sir W.
                                                  Scott.

Source : WordNet®

prolusion
     n 1: a short introductory essay preceding the text of a book
          [syn: {foreword}, {preface}]
     2: exercising in preparation for strenuous activity [syn: {warm-up},
         {tune-up}]