The phrase "massive immigration" refers to a significant influx or large number of people moving from one country to another to settle permanently. Full definition
«Yes, there is definitely a link between massive immigration... and radical Islam.» (businessinsider.com)
I think Europe has finally realized that Pandora's Box has been opened, when they allowed massive immigration from the Muslim nations... and will pay the price... sadly. (religion.blogs.cnn.com)
Ironically, such proposals come at a time when this form of government, which is but 200 years old, has been expanding rather than restricting freedom for all its citizens, and has been doing so despite massive immigration, legal and illegal, and despite having added «foreign» territories like Hawaii and Alaska. (religion-online.org)