When one deletes a friend from Facebook because he or she knows that the Facebook friend in question would eventually delete them instead. Preemptive unfriending thus robs the deleted Facebook friend of the joy of being able to delete them.
John: Why'd you delete Bec from you friend list?
Adam: I knew she'd eventually delete me so I wanted to take the satisfaction of unfriending for myself.
John: Ah, a preemptive unfriending.
The shit you take before you go out at night. Failure to take one can result in holding back a fart or even a shit in front of girls or others. Taking a preemptive allows for maximum beer drinkage and room for a late night meal.
Johnny: "Yo dude when these girls leave I'm gonna rip a sick fart."
Bobby: "Dude you defintely didn't taje a preemptive shit. We're going to the diner in a little bite."
Johnny: "Fuck!"
A phone call you make to your needy girlfriend/boyfriend before you get into a Do-Not-Disturb mode. The primary (albeit unspoken) purpose of the call is to momentarily assuage your girlfriend/boyfriend's urge to call you, thus decreasing the likelihood of them calling you later, when you can't afford to be distracted.
Peter: I gotta do my taxes, but I bet my clingy girlfriend won't be able to fight the usual urge to call me.
Lawrence: Dude, just turn the damn cell phone off, or, better yet, make a preemptive call and get it over with.
What you do when you are taking such a big dump that you are afraid you will clog the toilet, so you flush while the dump is being made. What you do when you expect a "Clogger Shit."