The Jargon File (version 4.4.7, 29 Dec 2003):

FidoNet
 n.

    A worldwide hobbyist network of personal computers which exchanges mail,
    discussion groups, and files. Founded in 1984 and originally consisting
    only of IBM PCs and compatibles, FidoNet now includes such diverse machines
    as Apple ][s, Ataris, Amigas, and Unix systems. For years FidoNet actually
    grew faster than Usenet, but the advent of cheap Internet access probably
    means its days are numbered. FidoNet's site count has dropped from 38K
    nodes in 1996 through 15K nodes in 2001 to 10K nodes in late 2003, and most
    of those are probably single-user machines rather than the thriving BBSes
    of yore.


The Free On-line Dictionary of Computing (30 December 2018):

FidoNet

    A worldwide hobbyist network of
   personal computers which exchanged e-mail, discussion groups,
   and files.  Founded in 1984 and originally consisting only of IBM
   PCs and compatibles, FidoNet grew to include such diverse
   machines as Apple IIs, Ataris, Amigas and Unix systems.
   Though much younger than Usenet, by early 1991 FidoNet had
   reached a significant fraction of Usenet's size at some 8000
   systems.

   [Jargon File]

   (2014-11-08)