/ ɪnˈkɜːʃn; NAmE ɪnˈkɜːrʒn/ noun incursion (into sth) ( formal )
1.
a sudden attack on a place by foreign armies, etc.
2.
the sudden appearance of sth in a particular area of activity that is either not expected or not wanted
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WORD ORIGIN
late Middle English (formerly also as encursion ): from Latin incursio(n-) , from the verb incurrere , from in- towards + currere run.