when someones head is so small their eye brow line meets their hair line.
Gawd Damn... Fucking niggas forehead so small.. Its a onehead
by AdurpaDoo August 31, 2009
Since a fivehead is extra forehead on top of a forehead, a onehead is a quarter of a full forehead. A forehead that rests somewhere at or just above the eyebrows. If the one who has a onehead shaves their head and has protuding round ears, they look like a baby chimpanzee.
That guy has a onehead, not a forehead.
by Solid Mantis April 3, 2021