the type of smile that is shaped like a frown but is obviously a smile. shown as a curling in the lips while over exaggerating a frown. either used as a visual, "touche" or an expression of contempt. sometimes accentuated with a raised eyebrow and/or a slight elevation to one side of the mouth or the other.
fryle
... and i could totally tell she wrecked her car just to impress me.
well what did you do next brah?
Someone who frown-smiles. They either do so because 1) they are not confident enough to smile, or 2) they want to create the impression of modesty and ingenuousness. This latter reason is usually a means to a particular end, for instance frown smiling in order to convince an audience of a statement or belief.