Definition of Waterloo, Battle of
a battle fought on June 18, 1815, near the village of Waterloo (in what is now Belgium), in which Napoleon’s army was defeated by the British (under the Duke of Wellington) and Prussians. The allied pursuit caused Napoleon’s army to disintegrate entirely, ending his bid to return to power.
(as noun a Waterloo
) a decisive defeat or failure:his team met their Waterloo