It's famous as the symbol of the pirate flag known as the 'Jolly Roger.' Today, it's used as a powerful international symbol to warn of deadly danger, like a chemical hazard warning.

Unlike the 💀 emoji, which is often used to mean laughter, this emoji still strongly retains its original meaning of 'dangerously fatal.' Therefore, it's sometimes used metaphorically to emphasize that something is extremely good or bad, like 'This food is fatally delicious.'