The delightful moment when a young lady shows off her knickers and/or poonani due to the happy union of high wind and flowing skirt.
Can also be attributed to short skirtism, especially when skirt wearer is sat on steps, usually eating sushi while reading an emo novel waiting for her next lecture to start.
See also DBA (Down-Blowse Action).
"OMG, the wind just picked up while I was walking down the street, minding my own, and this lovely pre-nugget's dress blew up in the air, and I got an eye-full of whaletail."
"USA, USA, USA, USA" (chanted by a bunch of blokes having just witnessed a wind-assisted skirt hike)