Definition of topples:
(v) :
(transitive) To push or throw over.
(v) :
To overturn.
(v) :
(figurative) To overthrow something.
(v) :
(intransitive) To totter and fall, or to lean as if about to do so.
(n) :
(informal) A fall (an instance of falling over).
(n) :
A cascade of dominoes falling, such that each fall causes the next domino to topple.