I'm a scholar of Arabic, and one of the most impressive things on my CV is the fact that I worked on the one of the major Arabic dictionaries, produced by a major publisher. It's not necessarily relevant to my future employment (I'm not seeking lexicography jobs), but it establishes me as an expert in the language. But I am very unsure about where exactly this should go on my CV. I haven't found any guidelines or relevant advice online because (unsurprisingly) not that many people write dictionaries.
I've done it three different ways in the past, and I'm not sure which is best:
Listed in "Publications." This is nice and prominent, but I'm not sure if some might consider it illegitimate. My name is not on the cover (the editor's is); I'm listed inside as one of the Arabic–English "Revising editors." I was the lead revising editor, I worked on the project for longer than any other (I probably wrote or revised over half the entries) and trained the other reviewers, but this information is not reflected in the job title.
Listed in "Professional appointments". This way treat it as a job rather than as a publication, with the dates that I was working on it as dates of employment. (I was a contract worker and the publisher was paying me by the hour.) But it's not an academic appointment or directly related to the job I'm applying for, so I'm not sure if this would be considered a legitimate place for it.
Listed in "Other Arabic experience" or something like that towards the bottom of the resume. No one would question the legitimacy of this placement, but it seems unfortunate to bury something so prestigious.
In my opinion, you should list your achievement in two places in your CV:
Under your "Work Experience" section: mention the period during which you worked as lead revising editor for the book, even if you didn't receive any payment/salary for it. Mention the title of the dictionary on which you worked on.
This dictionary should also be listed under "Publications", more specifically in a sub-section titled "Monographs (Co-edited works)", so as to distinguish it from any other books that you may have published as leading author/chief editor. In the bibliographic reference for the book, you may put the name of the chief editor(s), and right after that, write the names of the first 4 co-editors (in the same way as you would write the bibliographic reference for a book's translators), including your name, perhaps with an underline to emphasize your participation. Or, alternatively, you could just mention the chief editor, but right after the bibliographic reference, add a "Note:" mentioning that you were one of the main revising editors. If it is possible in any way to include page ranges for the parts/book sections that you worked in, please do so.