Today's OneWord: Cracked

I knew that eventually, the teacher was bound to crack. And he cracked. The first clue was that he walked into the classroom without a necktie on. His shirt's top two buttons were undone, exposing the initial tuft of untamed chest hair. The second clue was the fact that he remained standing in front of the class, rather than collapsing into his desk as if our very presence winded him. The third, well, that was obvious - the veins in his eyes were as large and red as Hell's tunnels.