Absurd dictionary is a theoretical dictionary that could define the words so deeply, that suddenly language stops making sense.
The back idea is that our reality and meanings of the world are a tautological fallacy. It consists on a dictionary that displays the recursive nature of concepts: how our concepts are sustained in other concepts.
Imagine somebody that wouldn’t know any word in our language nor any of our concepts, and starts learning them by using a dictionary, from scratch. When this person would seek a word and read it’s definition, would not understand it unless he read the definitions of the words that are used as definition.
In this dictionary, the words are not only defined, but also replaced by their definition while keeping grammatical consistency; forming a larger definition of the same initial word. This leads to a never ending game of diving into concepts, until the definition phrase lacks meaning. What starts being a short definition, ends up being an unutterable, long and recursive description.
See it in it’s current development state here