a battle fought on 18 June 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

a decisive defeat or failure

the coach rued the absence of his top player as his team met their Waterloo

he urged his fellow party members to dig in their heels and create a Waterloo for the president