Jøk is slang for dumbass and is used in a double sense; It's at the one side used for making a fool out of the offended, and at the other side used for making a fool out of those who get hung up in it's deliberated misspelling.
Matt: Every jøk should know how to use e=mc^2
Tore: You're stupid for mispelling "gjøk"
Matt: Who's stupid now, dumbass!
The Urban Dictionary Mug
One side has the word, one side has the definition. Microwave and dishwasher safe. Lotsa space for your liquids.
Buy the mug