cock a snook at someone/something

To regard someone or something with disrespect. Primarily heard in UK. Don't you cock a snook at my instructions—I'm your superior!

If you cock a snook at someone or something, you show them that you do not respect them, often by insulting them. They drove around in big cars, openly flaunting their wealth and cocking a snook at the forces of law and order. This was the electorate's attempt to cock a snook at their own political establishment. Note: To cock a snook at someone literally means to make a rude gesture by placing the end of your thumb on the end of your nose, spreading out your fingers, and moving them up and down. `Thumb your nose at someone' means the same.