A "sneer" is a facial expression that is typically characterized by raising one corner of the mouth while slightly turning up the nose, often accompanied by a scornful or contemptuous look. It is a mocking or contemptuous way of expressing disapproval or disdain towards someone or something. In other words, a "sneer" can be a dirty look given to show disrespect or mockery.
Note: The provided meaning of the answer is for the latest New York Times crossword puzzle clue: Contemptuous expression. Explanations are generated by AI and may be inaccurate.