hairline

(hârˈlīnˌ)

1. The outline of the growth of hair on the head, especially across the upper forehead and temples.
2. A very slender line.
3. Printing
   a. A very fine line on a typeface.
   b. A style of type using such lines.
4. a. A textile design having thin, threadlike stripes.
   b. A fabric, usually a worsted, with such stripes.