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pile Pelion on Ossa
1. To further complicate something that is already tedious or challenging. Ossa and Pelion are two mountains in Greece. A: "I told Becky you would pick her up." B: "I already have so much to do today—quit piling Pelion on Ossa!" Just when I thought I was almost done sorting these files, my boss piled Pelion on Ossa and brought me another box of them.
2. To do something that seems futile. I know that I'm just piling Pelion on Ossa by telling you to stay away from that boy, but I'm your father, and I don't want to see you get hurt. That couch will never fit up the steps—tell them to stop piling Pelion on Ossa!
heaping Pelion upon Ossa
Adding difficulty to difficulty; fruitless efforts. The reference is to the attempt by the giants in Greek mythology to climb to heaven by piling Mount Ossa upon Mount Pelion.