A mean girl is a female, usually a younger individual and not a grown woman, who is mean and who has an attitude towards others. Mean girl quotes can be found that show this type of female has self esteem issues, and this is why they need to treat others badly. A mean girl is one who picks on or bullies others just for fun, and who is not happy unless she feels superior to other females. Sometimes the most popular girl in high school is a mean girl but this is not always the case. The best way to deal with a mean girl is to ignore her, failing to give her the attention that she craves and refusing to play along with her games.