Source : Webster's Revised Unabridged Dictionary (1913)

Irruption \Ir*rup"tion\, n. [L. irruptio: cf. F. irruption. See
   {Irrupted}.]
   1. A bursting in; a sudden, violent rushing into a place; as,
      irruptions of the sea.

            Lest evil tidings, with too rude irruption Hitting
            thy aged ear, should pierce too deep. --Milton.

   2. A sudden and violent inroad, or entrance of invaders; as,
      the irruptions of the Goths into Italy. --Addison.

   Syn: Invasion; incursion; inroad. See {Invasion}.

Source : WordNet®

irruption
     n 1: a sudden violent entrance; a bursting in; "the recent
          irruption of bad manners"
     2: a sudden sharp increase in the relative numbers of a
        population
     3: a sudden violent spontaneous occurrence (usually of some
        undesirable condition); "the outbreak of hostilities"
        [syn: {outbreak}, {eruption}]