Hairline Ask Urban Dictionary about Hairline Share definition Flag The line where your hair starts. For some reason, dumbasses like to make fun of people's hairlines when they don't really matter. Kid: U HaVe a rachet hairline! Sane person: Why does it matter? Hairline by Racist21 June 3, 2015 0 0 Hairline Merch Get the Hairline mug. Buy Now — $32.95 See more merch