mine2c2 I "think" it refers to CD's like me ;) who wear them with or without padding or "falsies" that have not had cosmetic surgery or made any effort to increase their own natural breast developement, or absence of it.
Personally, I love the "feeling" of the clothing and it's a must for the transforming aspect of crossdressing. I use gel filled "pads" and fake breast shaped nipple enhanced balls to fill my bra and the visual effect is fantastic, though to enjoy nipple stimulation they have to "slip out" ;)
I might be wrong so, if anyone knows different please let us all in on it :)