Tap Pants
From Voyeurweb's Wiki about Sex
Tap pants are a form of Lingerie worn exclusively by women. It is also known by the names of French Knickers, Side-cut shorts, and Dance shorts. As the name implies, they are a type of shorts, in that they cover the pelvic area and the upper part of the upper legs.
Tap Pants look much like track shorts, allow freedom of movement, and can be worn as an outer garment over other types of underwear(G-Strings). However, most wearers may wear them as innerwear or leasurewear with nothing underneath. From a Distance, one could mistakenly identify Tap Pants as a Half Slip.