A sneer is a facial expression of scorn or disgust characterized by a slight raising of one corner of the upper lip, known also as curling the lip or turning up the nose. In The Expression of Emotions in Man and Animals, Charles Darwin defined a "sneer" as "the upper lip being retracted in such a manner that the canine tooth on one side of the face alone is shown" Darwin related the sneer to the snarl observed in non-human animals, particularly carnivores, observing that: It is suggested that the sneer is a universal expression of contempt and that Darwin was the first to observe this. Cats may be observed to sneer, though this is probably related to the Flehmen response.

In popular culture

'Did she take due warning, then?' asked Heathcliff, attempting a sneer. 'Did she die like a saint? (Chapter 16)|'Heathcliff did not glance my way, and I gazed up, and contemplated his features almost as confidently as if they had been turned to stone. His forehead, that I once thought so manly, and that I now think so diabolical, was shaded with a heavy cloud; his basilisk eyes were nearly quenched by sleeplessness, and weeping, perhaps, for the lashes were wet then: his lips devoid of their ferocious sneer, and sealed in an expression of unspeakable sadness. Had it been another, I would have covered my face in the presence of such grief. In his case, I was gratified; and, ignoble as it seems to insult a fallen enemy, I couldn't miss this chance of sticking in a dart: his weakness was the only time when I could taste the delight of paying wrong for wrong.' (Chapter 17)| I could doubt no more: he was dead and stark! I hasped the window; I combed his black long hair from his forehead; I tried to close his eyes: to extinguish, if possible, that frightful, life-like gaze of exultation before any one else beheld it. They would not shut: they seemed to sneer at my attempts; and his parted lips and sharp white teeth sneered too! (Chapter 34)