thumb (one's) nose at (someone or something)
1. Literally, to perform a rude gesture in which one touches their nose with their thumb in order to express contempt or a lack of respect. Did that guy really just thumb his nose at me? Do people still do that?
2. To openly display contempt or an intentional lack of respect toward someone or something. Don't thumb your nose at the boss if you want to keep your job!
thumb (one's) nose
To express scorn or ridicule, often by placing the thumb on the nose and wiggling the fingers.