: a sudden, violent, or forcible entry : a rushing or bursting in
… the assassination still feels like a primal catastrophe—an irruption of inexplicable evil as horrifying as any supernatural bogeyman.—Ross Douthat
: a sudden and violent invasion
… begins not with Hitler's attack on Poland, but with the Japanese irruption into Outer Mongolia in July 1939…—John Gooch
: a sudden sharp increase in the relative numbers of a natural population usually associated with favorable alteration of the environment
The owl's appearance came during an irruption, a huge southward migration of snowy owls from their arctic territories that, this year, followed a successful breeding period.—Scott Carroll
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