[Graham Boak]

The connecting rod goes between the piston and the crankshaft. As the piston goes up and down so the connecting rod makes the crankshaft rotate. The connection between the piston and the connecting rod is a circular bearing called the little end. The connection between the connecting rod and the crankshaft is a circular bearing called the big end. So a big end failure could be due to lack of lubrication and would be a disconnect between the connecting rod and the crankshaft, which probably would indeed lead to the piston jamming, or the rod flailing about inside the engine. It could simply be a material failure, rather than a lubrication failure.

Or perhaps I've forgotten more about engines than I thought...