General "frown":
* Kumunot ang noo (literally "the forehead wrinkled") - This is the most common and direct translation.
* Nag-asim ang mukha (literally "the face turned sour") - This conveys a more negative or disapproving frown.
* Nagsalubong ang kilay (literally "the eyebrows met") - This describes the physical action of frowning.
Other expressions:
* Nag-ngiwi - This can mean to grimace or frown in pain or disgust.
* Nagalit - This means "angry," which is a common reason for frowning.
Example sentences:
* Kumunot ang noo niya nang marinig niya ang balita. (He frowned when he heard the news.)
* Nag-asim ang mukha niya nang makita niya ang ginawa ko. (His face turned sour when he saw what I did.)
* Nagsalubong ang kilay niya nang magtanong ako sa kanya. (His eyebrows met when I asked him a question.)
The best word to use will depend on the specific situation and the level of formality.