The woman in the picture below is involuntarily making a hand gesture and striking a pose that is mocked by an insult called “Nose Thumbing”.
The woman is making the exact hand gesture and her body is holding the exact position it is because of changes to the structure of her body, not because she made a conscious willful decision to place all of the parts of her body in the exact locations they are.
Those structural changes to the body are associated with mental, emotional, and personality changes of a negative nature. So when someone voluntarily makes a Nose Thumbing gesture at another person, they are saying “You have the same mental, emotional, physical, and personality deficiencies as people who make this gesture involuntarily”.
Here is an example of someone making the insult gesture.
That gesture is not the exact way the Nose Thumbing insult is usually made. The man is hiding the full gesture because he is playing sports right in front of a camera. If someone became angry and wanted to cause him trouble for making the Nose Thumbing insult, he could legitimately claim that he is only raising a sore hand to his lips to soothe it.
Here is a man who is making something close to the Nose Thumbing Gesture because his body is changed in the way the Nose Thumbing Gesture is meant to mock.
One of the more obvious changes being referred to is the rotation of his head to his right so it looks like he is trying to focus mostly his left eye on the camera.