hairline (plural hairlines)
- The line along one's forehead where hair starts growing.
- It's just a receding hairline -- it's not like you're going bald.
- A very thin line in writing, drawing, or typography.
- A fishing line made from hair.
- A very thin fissure.
- While inspecting the new house, we found a few hairlines in one of the walls.
the line along one's forehead where hair starts growing