Juggernaut means a massive force. If the army marching into your country is a juggernaut, you're doomed. If you're trying to market a new Cola product, you're up against corporate giant Coca-Cola, a beverage juggernaut if ever there was one.
With its roots in Hindi, juggernaut originally referred to a crude statue from which the Hindu god, Brahma, turned into the living god, Krishna. There continues to be a festival in honor of this miracle, in which a statue of Krishna is carted through town. It is said that in times past, devotees would throw themselves under the cart’s wheels.