“Empty Discharge bottles / clear defication zone.”
I think this is a cute nod to one of the Doc’s quotes from the Call of the Dead easter egg. If you idle near the metal door between steps, you might catch him saying:
Call of Duty Zombies is a fan-managed gaming community centered around the popular Call of Duty franchise with central focus on the Zombies mode. Created in 2009, CoDZ is the ultimate platform for discussing Zombies theories, strategies, and connecting players.