Have you ever wanted to completely disable spell check function in CKeditor?
Well, after searching few hours for a solution, I ended up modifying the main plugin file, ckeditor.js, located in the CKeditor root folder (in my case, sites/all/libraries/ckeditor).
By default, this file is minified. If you try to beautify it, it might not work at all, so leave it minified.
Now, look after this string:
