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!