Bitch Face
From Super-wiki
Epic bitch face from Sam after he learns of Dean's relationship with Benny in 8.05 Blood Brother
"Bitch Face" is the term used by fans to describe a particular look of disapproval Sam gives Dean.
The phrase has become a Fanfiction cliche.
see also Puppy Dog Eyes
Sam has many other expressions too as analysed and documented by bellanut in Sam Winchester Mannerisms Pt1 and Sam Winchester Mannerisms Pt2.
