British slang term for the penis. Typically used as an excellent cheap insult. Used in jest (above "moron", just below "twat", and well below "cunt"), or used to describe someone who is doing something you think is annoying or a bit crap.
Scenario 1: one of your friends walks into the room and throws an apple at you. You reply: "Don't be a nob."
Scenario 2: your aging boss thinks he has broken his laptop because the battery ran out. You say: "Hah. He's such a nob."
Scenario 3: you have gonorrhoea, and it's making your nob hurt.