A distance of at least one unit of seating (e.g. a chair, a foot or two on a bench) in between you and at least one other person. It is most often used when: a) a foul odor is emanating from the person next to you b) you don't want to be accused of being too close to a person of the same sex for, well, obvious reasons...homosexuality c) discomfort
"Hey dude you smell like shit, we should have a 1 desk buffer zone or I'll pass out during class."
The empty urinal(s) between two guys using other urinals in a men's bathroom.
The bathroom was so crowded that I decided to use the stall instead of a urinal without a buffer zone.
The number of people needed in a group so you can enjoy yourself and not have to worry about having too much face time with *THAT* person in your circle (the frenemy, the "let's just be friends" ex, the hookup that turned out to be a really bad idea, the tool, etc)
Damn, Kelly responded to Rob's Taco Tuesday invite too; looks like only four of us. Let me ask Zak and Sara so there's a buffer zone.