Pinstripe is a term used to describe a narrow, vertical stripe that is typically found on clothing or other items. The name comes from the fact that these stripes were originally made popular by the pants worn by baseball players in the early 20th century, which had thin stripes resembling those of a pin-striped suit. Today, the term "pinstripe" is often used to refer to any item with narrow vertical lines, such as clothing, paper, or even cars.