The Fictionary provides spoiler free X-Ray experience
Fictionary currently works on e-ink Kindle devices,Kindle iOS apps (iPad/iPhone), and any software that can use the StarDict format such as the FBReader and Moon+ Reader Android Apps (requires ColorDict). Other e-reader such as the Nook do not allow easy switching to custom dictionaries either and store the dictionaries in a database format instead of an easier to create ebook format. I like the fact that unlike X-Ray, this system works across many different platforms.