A 'plebeian' is one of the common people. This is commonly abbreviated to 'pleb'. The public are the common people.
Therefore the 'Plebic' or the 'General Pleblic' is a combination of plebeian and public.
The general pleblic won't understand it.
Used to describe a state of pseudo rejection on Facebook, whereby someone has placed you on a 'restricted' list such that you remain a 'friend' officially, but can only see postings that they make public to the billion plus other a-holes with a Facebook account. Named after the plebeian class in ancient Rome who were deemed unworthy to mix with the nobility.
"I thought you guys were friends."
"On Facebook? Officially we are, but in name only. Really, he's part of the general pleblic."