That one guy at every high school or university who has mad long hair that's taken him forever to grow out. Everyone knows him by his hair and it's pretty much his dominant physical feature.
Most guys go through a shaggy phase, but a real hair boy grows his hair over a period of years and would never cut it even though he gets teased about cutting it all the time.
He's probably proud of his hair to the point of being annoying. You almost just want to chop it off.
"We saw that one kid. I can't remember his name. The one with the really long hair. That hair boy."
"Oh, that's Dylan."
"Yeah, him. His hair is insane."
"Yeah, he's been growing it since like 8th grade."
"He kind of needs a trim."
"Don't count on it."