What is the definition of visual facial expression?
can a symbol be a facial expression ?

A visual facial expression is a form of emotion displayed by the features on one's face. As I am typing this response, I notice my brows furrowing and my eyes narrowing as I try to create a reply. 

I believe that a symbol can evoke a facial expression, but I'm not entirely sure if it can be one on it's own. That is unless it's a picture of a face or an emoticon (emoji)

Only if that could happen to everyone

The details that best show evidence of tribal traditions are, "never in the history of his people had a man married a woman who spoke a different tongue” and "it has never been heard," was the verdict of an old man speaking a few weeks later.