Pomosexual
A pomosexual does not identify with, embrace, or fit into any of the conventional sexual orientations but rather rejects them.
Origins of the Term
From the book PoMoSexuals: Challenging Assumptions About Gender and Sexuality by Carole Queen and Lawrence Schimel, published in 1997.
The "pomo" part of the word is short for post modern, an art movement that rejected modernism and embraced eclecticism and combinations of things not previously brought together.
References
Updated Updated