A Terelak is someone who is grumpy most of the time. To strangers he seems unapproachable and quite morose. To outsiders watching in, he can seem bored and disorientated. To those who know him, he often dishes out bants left right and centre. Often after a big night out a Terelak will come to work late, unshaven, wearing the same clothes (or a similarly grotty and unironed item) and being even more grumpy than usual. A classic Terelak tactic after such nights is to not wear his jacket, therefore making it look like he's been at his desk and is not actually late.
Terelak's often use vocab no-one understands. It is essential that a dictionary is relied on when talking to a Terelak.
"I did a Terelak last night, lost my keys, my phone, my life!"
"Why is that guy so angry looking?"
"Oh, I wouldn't worry, he's just a Terelak"