What is women's lingerie?

Clothing not meant to be seen (except in private): underwear, nightgown, etc., usually of the silky and lacy variety.

Some styles of lingerie like the baby-doll or the chemise are frequently being seen as outerwear now. There is an exception to the rule about lingerie only being for private viewing, if you are a Hollywood star, then this can be the exception but other not so famous individuals have also tried this underwear as outerwear style.