Middle-lowered (Eyebrow position)
When the middle of the eyebrows are pulled down so they slope inwards, this often shows that the person is angry or frustrated. It can also indicate intense concentration (http://changingminds.org/techniques/body/parts_body_language/eyebrow_body_language.htm).
Glaring or eyes 'aglare.'
Glare: stare in an angry or fierce way, e.g."she glared at him, her cheeks flushing (https://www.merriam-webster.com/dictionary/aglare)."
Google Aglare: glaring - "his eyes aglare with fury." First Known Use of - 1712, in the meaning [previously] defined.
The beauty accidentally stood on Cruz's flowing ivory gown, prompting aglare from the actress.Cruz,32, had started the evening all smiles as she arrived at the American Film Institute's screening of her film Volver in Hollywood.
He stands up straight in his cage with his bright blue eyes aglare and shrieks in a perfect rage [and] braces his tough blue feet Maria do Carmo, please, give him a piece of raw meat-- Marianne, loan me a noun!
Selections from Edgar Allan Poe & The Juke-Box (https://www.thefreedictionary.com/aglare)
As nouns the difference between frown and glare is that frown is a facial expression in which the eyebrows are brought together, and the forehead is wrinkled, usually indicating displeasure, sadness or worry, or less often confusion or concentration while glare is (uncountable) an intense, blinding light. As verbs the difference between frown and glare is that frown is to have a on one's face while glare is to stare angrily (https://wikidiff.com/frown/glare).
As an adjective glare is (us|of ice) smooth and bright or translucent; glary.