If someone or something topples somewhere or if you topple them, they become unsteady or unstable and fall over. He just released his hold and toppled slowly backwards Winds and rain toppled trees and electricity lines. Topple over means the same as topple. The tree is so badly damaged they are worried it might topple over
To topple a government or leader, especially one that is not elected by the people, means to cause them to lose power. the revolution which toppled the regime. = overthrow