Frowny

From a late chapter of Bonnie Garmus’s sharp and delightful novel Lessons in Chemistry:

Then he swiveled his head toward a frowny-looking older woman holding a clipboard. 

Bonnie Garmus has said her book is about balance* in the way that chemistry itself is the science of balance.  Frowny is a word that assists in achieving tonal balance.

* The gorgeous novel A Fine Balance, by (the musical theatre–appreciating) Rohinton Mistry, is also about balance.