the arch of hair above each eye
"She raised her brow to shield her eyes from the bright sunlight."
The ridge over the eyes; the eyebrow.
"She raised her brow to squint against the bright sunlight."
To bound or limit; to be at, or form, the edge of.
"The captain ordered the surveyor to mark off the land where the river's brow began and ended its course along the valley floor."
A surname.
"The local bakery is owned by a Mr. Brow who has lived in the neighborhood for over thirty years."