WordWeb Online

1. The act of invading; the act of an army that invades for conquest or plunder
    
2. Any entry into an area not previously occupied
   "an invasion of locusts";
   - encroachment, intrusion
    
3. (pathology) the spread of pathogenic microorganisms or malignant cells to new sites in the body
   "the tumour's invasion of surrounding structures"

Derived forms: invasions

Type of: entering, entrance, incursion, penetration, spread, spreading

Encyclopedia: Invasion, Planeshift, Apocalypse