[sis-uh-fuh
s] 
| a son of Aeolus and ruler of Corinth, noted for his trickery: he was punished in Tartarus by being compelled to roll a stone to the top of a slope, the stone always escaping him near the top and rolling down again. |
A king in classical mythology who offended Zeus and was punished in Hades by being forced to roll an enormous boulder to the top of a steep hill. Every time the boulder neared the top, it would roll back down, and Sisyphus would have to start over.
Note: A difficult and futile endeavor may be called a “labor of Sisyphus” or a “Sisyphean task.”