To not wear any underwear.
from: "no" + "undies"
Sarah wanted to feel the breeze, so she wore nundies to school today.
After the catch phrase of Australian entrepeneur Kevin "Big Kev" McQuay who would wear massive lairy shirts (to fit his massive frame), most often one that was styled on the Australian flag. He would advertise his 100% Australian made and owned cleaning products by saying "I'M EXCITED!!!!"
After losing a lot of weight, and after resigning from his flailing business, Big Kev died of a heart attack in 2005.
When Jono heard his mates talking about the latest Jessica Alba film, he got a little bit Big Kev.