Noah Webster's New International Dictionary of the English Language

1. (v. i.) To show contempt by turning up the nose, or by a particular facial expression.

2. (v. i.) To insinuate contempt by a covert expression; to speak derisively.

3. (v. i.) To show mirth awkwardly.

4. (v. t.) To utter with a grimace or contemptuous expression; to utter with a sneer; to say sneeringly; as, to sneer fulsome lies at a person.

5. (v. t.) To treat with sneers; to affect or move by sneers.

6. (n.) The act of sneering.

7. (n.) A smile, grin, or contortion of the face, indicative of contempt; an indirect expression or insinuation of contempt.