Someone that is not attracted to anything, be it man or woman. Emos often claim to be zsexual, though are most likely lying.
Straight Friend: Hey, check out that hot chick over there!
Zsexual: I'm not interested in girls...
Gay Friend: Then what about that cute guy?
Zsexual: I don't like guys either.
A person you hate intensely not because they deserve such hatred but because they serve as a focus for your general hatred. A healthy way to dispense with excess animosity.
Jake's not really that big an asshole. He just serves as my hate sink.