Browband

Noun

1. Part of a horse's bridle that runs from just under one ear, across the forehead, to just under the other ear, preventing the bridle from sliding down.
2. A band of fur of a contrasting colour on an animal's brow.

   "Diana monkeys are generally black or dark grey, but have a white throat, crescent-shaped browband, ruff and beard."

3. A band of metal, part of a (person's) helmet or crown, which covers the brow.