take a nose dive
To plummet; fall sharply.
The stock market took a nose dive after the news of the President's heart attack.
thumb one's nose
To hold one's open hand in front of one's face with one's thumb pointed at one's nose as a sign of scorn or dislike.
After Bob ran into the house he thumbed his nose at Tom through the window.
To look with disfavor or dislike; regard with scorn; refuse to obey. Used with at.
Betty thumbed her nose at her mother's command to stay home.
Mary thumbed her nose at convention by wearing odd clothes.
turn one's nose up at
To scorn; snub; look down at somebody or something.
I don't understand why Sue has to turn her nose up at everyone who didn't go to an Ivy League college.
turn up one's nose at
To refuse as not being good enough for you.
He thinks he should only get steak, and he turns up his nose at hamburger.
under one's nose
under the nose of
In sight of; in an easily seen or noticeable place.
The thief walked out of the museum with the painting, right under the nose of the guards.
When Jim gave up trying to find a pen, he saw three right under his nose on the desk.