What is the meaning of the idiom 'herculean task'?

Hercules is a famous Greek mythological character known for his superhuman powers of strength. He was supposedly the son of the god Zeus, and thus had abilities that normal humans did not have. At one point, Hercules was given a series of twelve horribly difficult tasks that he had to perform in order to atone for killing someone - a herculean task is one that would have been given to Hercules because it is such a huge job.

An effort requiring more than usual strength or will power.