Patanties
pajamas and panties at the same time.
It is what you say when you want your roommates boyfriend to leave so you can get dressed. You will need to undress so you will be in your panties and then put on your pajamas. It is just a simpler way of saying "I'm getting undressed and ready for bed, please leave." So instead you say "Patanties!" and he will leave not knowing what just happened.