The opening of a women's poorly designed button-up shirt, between the breasts, that allows anyone from a side angle to catch a peek.
Woman Colleague: "Thanks to our company's poor choice of women's work shirts for this tradeshow, or a lack of understanding that women are curvier than men, I've been inadvertently playing peekaboob all day with customers"
Male Colleague: "Ya, but your sales are up..." (said with an envious tone...)