Source : Webster's Revised Unabridged Dictionary (1913)

Scenario \Sce*na"ri*o\, n. [It.]
   A preliminary sketch of the plot, or main incidents, of an
   opera.

Source : WordNet®

scenario
     n 1: an outline or synopsis of a play (or, by extension, of a
          literary work)
     2: a setting for a work of art or literature; "the scenario is
        France during the Reign of Terror"
     3: a postulated sequence of possible events; "planners
        developed several scenarios in case of an attack"