n. The action of irrupting or breaking into; a violent entry or invasion; an inbreaking; an intrusion.
n. An abrupt increase of numbers of a particular animal.
the GNU version of the Collaborative International Dictionary of English
n. A bursting in; a sudden, violent rushing into a place.
n. A sudden and violent inroad, or entrance of invaders.
The Century Dictionary and Cyclopedia
n. A bursting in; a breaking or rushing into a place; a sudden invasion or incursion.
n.Synonyms Foray, raid.
WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
n. a sudden violent spontaneous occurrence (usually of some undesirable condition)
n. a sudden sharp increase in the relative numbers of a population
n. a sudden violent entrance; a bursting in
Word Usage
"The white, two-foot-tall birds, which live in the Arctic the rest of the year, are known to fly south in large numbers every few winters in what is known as an irruption."