The act of deliberately waiting to write a post or comment, so that you can avoid commenting on it immediately after it was written. This act makes it look like you're busier than you really are, instead of revealing the fact that you are on facebook constantly.
Can also be used for texts, emails, chats etc.
Friend #1: DUDE check this out!! This is totally cool! (link)
...wait...
...wait...
Friend #1: hello? are you there?
Friend #2: oh hey, yeah that's awesome, sorry I was busy working.
Friend #1:no you weren't working, you were pulling a Post Wait on me!