"
She was lookin' kinda dumb
With her finger and her thumb
In the shape of an L on her forehead...
Well
When you place your finger and your thumb on your forehead in the shape of the letter "L" is commonly referred to as a hand signal saying "loser. "The girl being referenced in the song was doing this pose, but the song also implies that she was looking uneducated and stupid by doing so.