invade in WordNet English dictionary

1. to intrude upon, infringe, encroach on, violate
   "This new colleague invades my territory"; "The neighbors intrude on your privacy"
   intrude on  invade  obtrude upon  encroach upon 
   
2. occupy in large numbers or live on a host
   "the Kudzu plant infests much of the South and is spreading to the North"
   invade  overrun  infest 
   
3. march aggressively into another's territory by military force for the purposes of conquest and occupation
   "Hitler invaded Poland on September 1, 1939"
   invade  occupy 
   
4. penetrate or assault, in a harmful or injurious way
   "The cancer had invaded her lungs"
   invade