1. 迁出城市的过剩人口
Overspill is used to refer to people who live near a city because there is no room in the city itself.

2. 过多的物品（或人）；无法容纳的物品（或人）
You can use overspill to refer to things or people which there is no room for in the usual place because it is full.

1. the occurrence of surplus liquid (as water) exceeding the limit or capacity

Synonym: overflowrunoff

2. the relocation of people from overcrowded cities
they are accommodated in new houses or apartments in smaller towns