The ock in your typical local community college class who resists (in the classroom) expressing himself or liberally speaking to people unless called on. He is typically sleepy-eyed with perma-frown/stance and at any and every alloted break, this guy will jump on the cell phone and become a totally different person. see also total dick and indistinguishable.
Sally: That guy in our Chem class seems shy, I wonder if I should go talk to him?
Alex: I killed some vagrants last Tuesday.