To take the sexyness out of someone or something.
Your bed is almost sexy, but something is desexifying it.
The act of taking someone's sexyness away. Desexification can include Shaving one's Facial hair, chest hair, or dumping acid on a face.
When you have known a person for too long or they are of a certain kind so you have a moral dilemma to not fuck them.
I would have sex with her, but she is my sister so she is Desexified