"Five O'Clock Shadow" refers to the stubble that appears on a man's face several hours after shaving. It typically becomes noticeable in the late afternoon or early evening, around five o'clock, hence the name. This shadow is caused by the regrowth of facial hair, which can create a darker appearance on the skin. The term is often associated with a rugged or casual look, and it has been popularized in fashion and media. Many men intentionally maintain a stubble style for its aesthetic appeal, while others may simply not have time to shave throughout the day.