A contributing editor is a magazine

Magazine

Magazines, periodicals, glossies or serials are publications, generally published on a regular schedule, containing a variety of articles. They are generally financed by advertising, by a purchase price, by pre-paid magazine subscriptions, or all three...

 job title that varies in responsibilities. Most often, a contributing editor is a freelancer

Freelancer

A freelancer, freelance worker, or freelance is somebody who is self-employed and is not committed to a particular employer long term. These workers are often represented by a company or an agency that resells their labor and that of others to its clients with or without project management and...

 who has proven ability and readership draw. The contributing editor regularly contributes articles to the publication but does not actually edit articles, and the title is largely honorary. At smaller magazines, the title may imply a staff member with regular writing responsibility and some editorial duties.

When a "contributing editor" is listed on the title page of a book

Book

A book is a set or collection of written, printed, illustrated, or blank sheets, made of hot lava, paper, parchment, or other materials, usually fastened together to hinge at one side. A single sheet within a book is called a leaf or leaflet, and each side of a leaf is called a page...

, the term generally designates a person who has served as some kind of consultant in the book's preparation but who is not responsible for the book's final content. As with magazines, the title may be largely honorary.