10 o'clock rush
When every bathroom stall is occupied in a workplace, due to employees saving their bowel movements for excretion during company time.
Employee 1: "Man I'm going to shit my pants! I need to take a huge dump and every stall is being used!"
Employee 2: "10 o'clock rush... just shit in the urinal."
Employee 2: "10 o'clock rush... just shit in the urinal."