smartass face 

or SAF

A face which people display when they pretend to know it all when they do not. Usually used when bsing.

Connie's smartass face appears as she answers the question.

smartass face by kkling October 20, 2010

Resting smart ass face 

When someone who is normally a smart ass is currently not saying or making a face which would normally be interpreted as being a smart ass.

David Jones is a prime example of resting smart ass face when he isn’t speaking.

Resting smart ass face by Clvegrl March 29, 2020