"In the online communities of projects such as Wikipedia and OpenStreetMap, an edit-a-thon (sometimes written editathon) is an event where editors get together to edit and improve a specific topic or type of content, typically including basic editing training for new editors. The word is a portmanteau of “edit” and “marathon”.
Wikipedia edit-a-thons have taken place at Wikimedia chapter headquarters or cultural institutions such as museums or archives, and included topics such as cultural heritage sites, museum collections, women’s history, art, feminism, narrowing Wikipedia’s gender gap, and other topics. Some have been organised by Wikipedians in residence.
The OpenStreetMap community has also hosted a number of edit-a-thons." (http://www.co-creative-recipes.cc/recipes/edit-a-thon/)