The act or acts of using public information networks such as newscasts or newspapers in a misleading, devious, or mischievous way, to disperse a hidden propagandic message that seems plausible to the population.
First usage:
Coined by Bob Corduroy on Comedy Central’s “The Daily Show”, Wednesday 17th of March 2004.
The word has gotten mainstream acceptance with its use in an Op-Ed column by Frank Rich of the New York Times.
UPDATE: Geoff Nunberg has found older citations:
As it happens, “infoganda” has been around for a while — it first appeared in the press during the Gulf War of 1991 as a name for the reports and footage that the Pentagon was furnishing to journalists.1 But the word may very well have been independently coined on several occasions.