Sometimes being angry can be overwhelming. Driving during rush hour traffic can lead to angry confrontations. Flipping the middle finger in America or the “inverse peace sign” in the United Kingdom can speak volumes (thanks for the embarrassing moment former President Richard Nixon).
In Greece, they have their own unique way to tell you to go to hell. Showing someone your outstretched palm is considered to be very rude and vulgar. The palm gesture can mean a slew of things, so it is best to avoid showing someone your palm in an angry manner.