Source : Webster's Revised Unabridged Dictionary (1913)

Incursion \In*cur"sion\, n. [L. incursio: cf. F. incursion. See
   {Incur}.]
   1. A running into; hence, an entering into a territory with
      hostile intention; a temporary invasion; a predatory or
      harassing inroad; a raid.

            The Scythian, whose incursions wild Have wasted
            Sogdiana.                             --Milton.

            The incursions of the Goths disordered the affairs
            of the Roman Empire.                  --Arbuthnot.

   2. Attack; occurrence. [Obs.]

            Sins of daily incursion.              --South.

   Syn: Invasion; inroad; raid; foray; sally; attack; onset;
        irruption. See {Invasion}.

Source : WordNet®

incursion
     n 1: the act of entering some territory or domain (often in large
          numbers); "the incursion of television into the American
          livingroom"
     2: an attack that penetrates into enemy territory [syn: {penetration}]
     3: the mistake of incurring liability or blame