The act of Facebook blocking your account, blocking you from making friend requests or stopping you from messaging.

Facebook can block you for any violation of TOS, either real or perceived.
Ken was F Blocked when he requested too many Facebook friends.

When Facebook determined the user violated their TOS, they F Blocked the user.
by Spanky Data Doctors January 25, 2012
To F block: To have sex with someone on your block or in your apartment complex.

F Blocking: To be having sex with someone repeatedly who lives on your block or in your apartment complex.
I could hear Rachael F blocking him through my window.
by F block gangsta February 10, 2010