You may not know the "look," but it's definitely part of a teenager's demeanor.
"The look" is a facial expression that is used by adolescents to communicate with each other -- but even when you recognize it, it means different things to different people.
A group of researchers studied "the look" and found that, when it's used between friends of the same gender, it's meant to communicate anger, sadness or disgust. When it's used between non-friends of the same gender, it also means anger or disgust, but with an air of superiority attached.
They also found that when it's used with people of the opposite gender, it includes a message of power and authority.