An outfit or item of clothing either so complicated or so ugly that even a rapist wouldn't bother to try and do you.
* disclaimer: there are some sicko's out there that even a poncho and track pants won't stop.
2) An outfit or item of clothing so unattractive, it wards off potential rapists. E.g. 'This hoodie is so gross, it's such an A.R.D. but I don't care, I'm compfy.'. or 'Man, did you see what she was wearing?! Total A.R.D. '