“Megajournal” is a popular buzzword for a certain type of journal, employed mainly by publishers in the online, open access field. Megajournals contain articles from a wide variety of disciplines; they are a potpourri of many subjects, not a narrow slice of a big area. They are the opposite of specialty journals. Promoters of the term megajournal usually also tout quick response times, rapid publication, and open access to readers free of charge.
Megajournals: New Concept or Old Hat?
Really, megajournals are nothing new. Nature is a megajournal, so is Science, and the Journal of the American Chemical Society (JACS).