Original: The Running of the Bulls (in Spanish encierro, from the verb encerrar, to lock/shut up, to pen) is a practice that involves running in front of bulls that have been let loose on a course of a sectioned-off subset of a town's streets.
Simplified: The Running of the Bulls (in Spanish el encierro, meaning "the enclosing") is an activity that involves running in front of bulls on a course of a sectioned-off area of a town's streets.