
1) Anatomical ridges 2) Expressive facial features 3) Eye features 4) Foreheads 5) Groucho wiggled his 6) Hair above the eyes 7) High or low ones 8) They can get furrowed 9) They may be arched 10) They may be arched or plucked 11) They may be plucked 12) What some people knit 13) Wrinkled facial features 
Found on 
https://www.crosswordclues.com/clue/brows

The ridges formed above the eyes by frontal bone contours.
Found on 
http://www.akc.org/about/glossary.cfm

The ridges formed above the eyes by frontal bone contours.
Found on 
https://www.encyclo.co.uk/local/21273
  No exact match found.