AFJ

from Jargon File (4.4.4, 14 Aug 2003)

AFJ
 //, n.

   Written-only abbreviation for "April Fool's Joke". Elaborate April
   Fool's hoaxes are a long-established tradition on Usenet and Internet;
   see {kremvax} for an example. In fact, April Fool's Day is the only
   seasonal holiday consistently marked by customary observances on
   Internet and other hacker networks.

from The Free On-line Dictionary of Computing (8 July 2008)

April Fool's Joke
AFJ

   <humour, event> (AFJ) Elaborate April Fool's hoaxes are a
   long-established tradition on {Usenet} and {Internet}; see
   {kremvax} for an example.  In fact, April Fool's Day is the
   *only* seasonal holiday marked by customary observances on the
   hacker networks.

   (1995-01-25)

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