grudging look; resentful expression
A literary or somewhat formal noun describing a facial expression that shows resentment or a grudge. Not an everyday colloquial word; more likely in written descriptions or elevated speech.
He looked at me with a resentful expression.
At those words, a flash of resentment crossed her face.
Compound of 怨 (resentment, grudge) and 色 (color, expression). The exact historical derivation is uncertain, but the word follows a common pattern of combining an emotion kanji with 色 to mean 'look/appearance of that emotion'.