|1.||to enter forcibly or suddenly|
|2.||(of a plant or animal population) to enter a region suddenly and in very large numbers|
|3.||(of a population) to increase suddenly and greatly|
|[C19: from Latin irrumpere to rush into, invade, from rumpere to break, burst]|
irruption ir·rup·tion (ĭ-rŭp'shən)
The act or process of breaking through to a surface.