In Mandarin, it is "ku". The character is 酷

in mandarin: ku (tone 4) 酷 ,eg. you are so cool. 你很酷! in cantonese:ying(tone 2) 型(use "xing"tone 2 to type it with Pinyin）, eg.you are so cool. 你好型啊！

The Pinyin should be “kù” in Mandarin. I don't know Cantonese.