From WordNet (r) 3.0 (2006):
invade
v 1: march aggressively into another's territory by military
force for the purposes of conquest and occupation; "Hitler
invaded Poland on September 1, 1939" [syn: invade,
occupy]
2: to intrude upon, infringe, encroach on, violate; "This new
colleague invades my territory"; "The neighbors intrude on
your privacy" [syn: intrude on, invade, obtrude upon,
encroach upon]
3: occupy in large numbers or live on a host; "the Kudzu plant
infests much of the South and is spreading to the North"
[syn: invade, overrun, infest]
4: penetrate or assault, in a harmful or injurious way; "The
cancer had invaded her lungs"