Kant used the term "noumena" to oppose "phenomena": the noumenal you is inherently you despite the phenomenal appearance other people may see.
Zizek says the "noumenal core" of you is the unfathomable "x," the je ne sais quoi, the charismatic core. Drawing from Lacan, the petit objet a* creates your noumenal core, the desire that cannot be fulfilled, that drives you and bleeds out of you, which is experienced as charm, danger, or drive.
In this sense, you are more than you: you are your "x"—your excess. Beyond the phenomenal experience of "you," your noumenal core exudes and expands to become the undefinable "you" to which people react.
