This octagonal shape is a universal agreement. It means 'stop' in any country. So, even if you don't speak the same language, this single emoji can clearly convey an urgent message to cease an action.

Its design was made to be recognizable even from a distance or from behind. Because of this feature, it's effective for conveying a firm refusal or interruption in online chats without misunderstanding. You can use it for a friend's playful joke, like "Please, just stop 🛑."