A type of women's underwear, which preserves heat to ward off the cold. So-called because originally only "babaa" (a derogatory term meaning "elderly woman") wore them, and younger people regarded these undershirts with disdain. However, recently the shirts have become popular with fashion-conscious young women who want to be scantily dressed, and there is now a wide variety of colors and designs.
There are several points to consider when wearing these undershirts: Colors like beige or pink are good because they aren't see-through. A wide v-neck style is good because it won't show above your neckline, etc. And if you have a date, it's better to forget practicality, and to go for a glamorous lacey style. These undershirts aren't very popular with men, however. Japanese women must choose between catching a cold or attracting a man. Source: http://www.hiragananet.com/hiragananet/kiji_nihongo/kiji_b.htm