"truth which has been edited to suit the taste of the majority. aka 'majority truth'. Spawned by the popularity of user-edited sites such as wikipedia, wherein users can edit history as they please, the information remaining so long as others agree with them. consequently historical truth is altered to form 'wikitruth'."
This is mostly true, except for the historical truth part. While some believe that there is an objective truth which we can magically confirm to be absolutely true, the majority of truth that humans believe in has always been some form of Wikitruth.
Wikiality is another form of Wikitruth, as defined in a very similar way by political satirist Stephen Colbert.