1. something (such as a force, campaign, or movement) that is extremely large and powerful and cannot be stopped
2. a very large, heavy truck
Lookups for juggernaut spiked in the wake of Hillary Clinton and Donald Trump's primary victories on March 15:
But even Mondale carried his home state against Ronald Reagan in 1984 (albeit barely), something Rubio could not manage to do in the Florida primary, where Donald Trump’s triumphant juggernaut won all 99 Republican delegates on Tuesday.
—vanityfair.com, 15 March 2016
Rubio’s campaign raised eyebrows recently by urging Ohioans to cast ballots for Kasich as the best strategy to stop the Trump juggernaut.
—Dayton Daily News, 15 March 2016
Super Tuesday 2.0: Trump, Clinton juggernaut rolls on.
—Business Standard, 16 March 2016
Juggernaut came to the English language through stories of the Hindu god Vishnu—Jagannāth is one of his titles. At an annual festival in the city of Puri, objects representing Vishnu and his siblings are transported in enormous, lavishly decorated chariots. The festival is crowded with worshippers, and over the centuries there have been instances of pilgrims getting crushed. Travelers to India exaggerated these stories, and so the legend of fanatics throwing themselves before the rolling juggernaut to die was born.
This led to the word being used in a highly figurative fashion, referring both to a large, heavy vehicle (chiefly in British usage), or to any seemingly inexorable force. From very early on, juggernaut proved to be useful when describing political movements.
Surely, this man does not advise the federalists of this state to march in the rear and bend their knees to the great Juggernaut of democracy!
—The Maryland Gazette [Annapolis, MD], 30 August 1821
I do not hold, Mr. Editor, a share of bank stock, not do I apprehend myself to be more likely to bow before the shrine of either a political or pecuniary “Juggernaut” than this vehement foe to “monied aristocracy.”
—The New York Evening Post, 15 April 1822