Thats Cold.
Said to describe something someone has said/done that is very harsh or mean. Can be used funnily (See Example One) or can be used that its so mean its gone past being funny (See Example Two).
Example One
Person A: Oi Bens family is so poor, his mum sends him to kfc to lick peoples fingers.
Person B: *HAHAHAHH* Thats Cold man, Thats Cold. *HAHAHAHHA*
Example Two
Person A: Bens a dickhead, he should just drop dead, not like anyone will miss him in his grave!
Person B: Nah allow it man, Thats cold
Person A: Oi Bens family is so poor, his mum sends him to kfc to lick peoples fingers.
Person B: *HAHAHAHH* Thats Cold man, Thats Cold. *HAHAHAHHA*
Example Two
Person A: Bens a dickhead, he should just drop dead, not like anyone will miss him in his grave!
Person B: Nah allow it man, Thats cold