When one meets with their designated zombie-killing comrades at a specified time to deliver death to the undead. Usually (but not always) takes place in the world of online gaming.
~My Girlfriend: "Hey honey, do you want to come over to my place Friday night for dinner (winks)?"
~Me: "I have more important matters to attend to that night. Specifically, a zombie date with my brothers in arms at 19:00 hours."