breeding ground

Từ điển Oxford Advanced Learner 8th

ˈbreeding ground [breeding ground breeding grounds] BrE NAmE noun
1. usually plural a place where wild animals go to produce their young
•Some birds fly south to find good breeding grounds.
2. ~ (for sth) usually singular a place where sth, especially sth bad, is able to develop
•This area of the city has become a breeding ground for violent crime.