It has the same meaning as the person pouting (🙎) emoji, but it's more often used by women to express their feelings. It's effective for cutely showing that you're grumpy or sulking.

This expression is often seen on characters in East Asian pop culture, especially in anime or dramas, who are outwardly grumpy but warm on the inside. Therefore, this emoji is often taken as a cute signal meaning, 'I'm a little upset, so please notice,' rather than genuine anger.