Adjective:

1. of or relating to Sisyphus

2. both extremely effortful and futile

SISn.<非正式>姐妹(=sister)abbr.秘密情报处(=secret intelligence service)Siskn.西斯克

1. What they do is a Sisyphean task.
   他们所干的活是徒劳的苦役。