Synonyms:
deadpan, expressionless, impassive, poker-faced, unexpressive
Meaning: deliberately impassive in manner; "deadpan humor"; "his face remained expressionless as the verdict was read"
Usage examples
His tone was cold and his face expressionless.
Grant, his face an expressionless mask, presided, and said but little.
It's impossible." He called to the other men who were watching the unequal battle with expressionless immobility.
As I came back to myself I glanced at Sola, who had witnessed this encounter and I was surprised to note a strange expression upon her usually expressionless countenance.