I find Kindle's dictionary feature to be annoying - I've used Touch and Paperwhite, where I'm touching the screen all the time, and I frequently get an annoying pop-up definition I don't want.
Is there any way to disable the dictionary?
I think the only option you have is to delete the dictionary completely, thus disabling it. (Search for the dictionary on your device and remove it like any other book. You can re-download it later if there is the need.)