Humour and personality of an undesirable nature, conversational skills of an intolerable standard, the inability to integrate oneself into the flow of jovial nonchalence, inadvertantly depressing dialogue, sick, nasty or 'over-the-top' prankstery.
Person 1 - "That clown never shuts up about how fast his brother's car is or how much money his Dad earns"
Person 2 - "I know, shan banter"
Person 1 - "I had that cow moaning at me all night about how she's got no career and all her men have been pigs"
Person 2 - "Ooooooh, shan banter"
Person 1 - "Did you hear those sickos put cow dung in a super soaker and squirted a blind guy?"
Person 2 - "Seriously? Shan Banter!"