Which word refers to the appearance or expression of a face?

The term that refers to the appearance or expression of a face is "countenance." This word encompasses not only the physical look of the face but also the emotional and mental state that can be inferred from someone's facial expression. For instance, a person's countenance might reveal feelings of happiness, sadness, anger, or concern, thus serving as an essential form of non-verbal communication.

The other options have distinct meanings that do not relate to facial appearance or expression. "Cornucopia" refers to an abundance of good things, often represented as a horn overflowing with produce. "Connotation" pertains to the associated or secondary meaning of a word, beyond its literal definition. "Conciliate" means to placate or pacify someone, which relates more to conflict resolution than facial expression. Hence, countenance is the precise term for describing someone's facial appearance or expression.