—v.t. 1. to enter forcefully as an enemy; go into with hostile intent: Germany invaded Poland in 1939. 2. to enter like an enemy: Locusts invaded the fields. 3. to enter as if to take possession: to invade a neighbor's home. 4. to enter and affect injuriously or destructively, as disease: viruses that invade the bloodstream. 5. to intrude upon: to invade the privacy of a family. 6. to encroach or infringe upon: to invade the rights of citizens. 7. to permeate: The smell of baking invades the house. 8. to penetrate; spread into or over: The population boom has caused city dwellers to invade the suburbs.
—v.i. to make an invasion: troops awaiting the signal to invade.