to fall to the ground because of not being very well balanced or because of being pushed
Those books look as if they're going to topple over any minute.
phrasetopple over topple over • topple sth over to become unsteady and fall over, or to make something do this: The high wind just toppled the boats over.Mark had dirty dishes piled so high they looked like they were going to topple over at any moment.
topple over
[for something very tall] to fall over. I was afraid that Jimmy's stack of blocks would topple over.The stack of books toppled over and ended up as a jumbled mess on the floor.