The pre-lash party that occurs in the communal showers at the sports centre after a tough training session, involving booze, music, and showers.
Usually, it is used as an excuse to pre-drink for a big night out when training finishes late.
Girl 1: "What is all that music coming from the changing rooms?"
Girl 2: "Yeah, the basketball girls are having a shower party."
Girl 1: "Training ends pretty late tonight, I won't have time to pre-drink"
Girl 2: "Just come to the shower party!"