Hairline/ˈherlaɪn/ Definition 1 of 4Pro Tip 1/2Receding Hairline Often describes men's ageing or genetic hair loss starting near the forehead. His receding hairline made him look older than he was. Pro Tip 2/2Hairline and Attractiveness A full hairline is commonly seen as a sign of youth and attractiveness. Models in the magazine typically had perfect hairlines.