Underalls were a brand of undergarments for ladies marketed in the United States from their introduction in 1976 until the early 1990s. They were famous for being a combination of pantyhose and panties together, presumably to prevent panty-lines.
A prominent, visible panty line or VPL (visible panty line) occurs when the outline of one’s underpants becomes visible through one’s clothes. There may be a ridge or depression in the clothes, or the clothes may be slightly see-through. The taboo in many cultures against showing one’s underwear means that panty lines are generally considered undesirable and embarrassing.