Definition of "Invade" :

verb: march aggressively into another's territory by military force for the purposes of conquest and occupation

"Hitler invaded Poland on September 1, 1939."

verb: penetrate or assault, in a harmful or injurious way

"The cancer had invaded her lungs."

verb: to intrude upon, infringe, encroach on, violate

"This new colleague invades my territory."

verb: occupy in large numbers or live on a host