invasion invasion /ˌɪnˈveɪʒən/

noun

1. () The act of invading; the act of an army that invades for conquest or plunder  ( invasion )
   the act of invading; the act of an army that invades for conquest or plunder
     The army launched a surprise invasion on the enemy's territory.
   The army launched a surprise invasion on the enemy's territory.
   
2. () Any entry into an area not previously occupied  ( invasion , intrusion , encroachment )
   any entry into an area not previously occupied
    An invasion of tourists
   an invasion of tourists
    An invasion of locusts
   an invasion of locusts
   
3. (pathology) the spread of pathogenic microorganisms or malignant cells to new sites in the body  ( invasion )
   (pathology) the spread of pathogenic microorganisms or malignant cells to new sites in the body
    The tumor's invasion of surrounding structures
   the tumor's invasion of surrounding structures