Undeciphered writing system

An undeciphered writing system is a written form of language that is currently not understood. In this context, a writing system is used to mean a series of glyphs; these glyphs may represent writing in a language. However, this is not known until they are deciphered. 
Not being able to decipher a text can have several reasons:
There is also the concept of false writing systems: these are constructed sets of symbols that are meant to represent a writing system, but that do not.