Its a term for the amount of clothes you have on (or don't have on) when you anticipate being naked in the near future, to make becoming completely naked easier.
For example: When you know you are gonna have sex or take naked photos later in the evening, its when you remove any excess clothing (i.e. belts, jackets, extra shirts, and so on) so that you don't get tied up "when its that time"
John: Rachel, get pre-naked, i plan on taking naked pictures of you when you go to sleep.
Rachel: ok.
John: Rachel, get pre-naked, i plan on taking naked pictures of you when you go to sleep.
Rachel: ok.
by Audwin September 10, 2006