Fanfiction written on Twitter. So named because of the common use of hashtags on Twitter, and the common contraction of Fanfic for fanfiction.
Remember that cancelled show "Studio 60?" Well years later it got new life when some person or persons created a Twitter account for every single character, who then proceeded to live-tweet their fictional jobs. Though not the first example of hashfic, it's certainly among the most elaborate.
by President Warren G. Harding May 19, 2011