The pit is a sub-forum of www.ultimate-guitar.com.
The pit is a place where everything non-guitar/instrument related is put. Many users post internet memes, talk about sex, drugs, social problems, magazines, world news. Many people post "silly" threads in this section of the forums and they get "rapped" and "fapped" on.
I posted a reply to a thread in the pit called "If you put 'The Pit' in the dictionary..."