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1.
To deactivate your facebook account and not activate it for as long as you can until you give in.
Jennifer: Hey did Susan get rid of you also on facebook?
Tim: No, she just went on a Facebook Fast.
by RoseyPosey67 May 03, 2009
 
2.
Taking a break from Facebook when you realize you are spending way too much time there.
I had to take a Facebook fast because I was getting nothing done at work.
by PalmSprings09 August 13, 2010