: 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
b
: 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
c
ecology: 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
Recent Examples on the WebThe numbers are low for the middle of November, Brady said, and suggest an irruption, in which large numbers of owls move into Wisconsin and the U.S., is unlikely this year. Paul A. Smith, Milwaukee Journal Sentinel, 21 Nov. 2021 According to Rauch, the last irruption of snowy owls in the D.C. area was in 2014, when at least four were reported.Washington Post, 10 Jan. 2022 The reasons aren’t hard to imagine: the irruption of e-commerce and changes in consumer habits. Damian Scalerandi, Forbes, 8 Sep. 2021 The exact cause of an irruption is unknown and difficult to predict, although according to the DNR in recent irruption years more owls had been spotted by this time — 84 in 2017, 82 in 2015 and 44 in 2014. Chelsey Lewis, Milwaukee Journal Sentinel, 30 Nov. 2020 Opening Day, meanwhile, brings with it an irruption of promise for even the most hopeless teams that is more suitable for Easter. Matthew Walther, WSJ, 1 Apr. 2021 Some years, hundreds will migrate into the state in an event known as an irruption. Chelsey Lewis, Milwaukee Journal Sentinel, 30 Nov. 2020 This year’s extra-large migration, called an irruption, is notable even among similar events because the birds migrated at night, Andrew Del-Colle wrote for Audubon in October. Theresa Machemer, Smithsonian Magazine, 11 Mar. 2021 An irruption is a migration of large numbers of birds to areas where they aren't typically found.Star Tribune, 22 Dec. 2020 See More