To overpopulate means to fill an area with too many people or animals for it to support comfortably. When a region becomes overpopulated, there aren't enough resources like food, water, or living space for everyone there.

Think about what happens when too many students crowd into a classroom designed for twenty: it becomes noisy, cramped, and hard to learn. Similarly, when an island or city becomes overpopulated, people struggle to find housing, traffic becomes terrible, and basic services get stretched thin.

Scientists worry about rabbits overpopulating Australia, where millions of them eat crops and destroy native plants because they have few natural predators. Meanwhile, marine biologists study how jellyfish can overpopulating coastal waters when conditions favor their survival, disrupting the balance of ocean ecosystems.

The word doesn't mean “a lot of people,” it means too many for the available resources. A concert hall might hold 2,000 people comfortably, but if 3,000 people show up, it's overpopulated. The difference between populated and overpopulated is whether an area has enough of what its inhabitants need to thrive.