Fanaa in Arabic means annihilation or death. The word is used in some extreme levels of Sufism to refer to the state a mystic reaches in which they have union with God. it's the state of Nirvana in which all in this universe is leveled down and reduced to one principle immanent in the world.
To extreme Sufis in this state, God dwells in every thing. As a result, dualities like God/man, and man/nature disappear. And the holy becomes equal with the unholy, the human with the nonhuman, the sacred with the profane , the relative with the absolute, the good with the evil, the above with the below, everything with everything else. Eventually, everything becomes nothing.
In this state of fanaa, God has no meaning, and humanity has no purpose or any essential value in this life. This state of Fanaa only leads to a nihilistic view of life.
Reference: http://i-epistemology.net/attachments/414_V14N1%20Spring%2097%20-%20Elmesseri%20-%20Modernity,%20Immanence,%20and%20Deconstruction.pdf
