Is this Chinese and what is the meaning: 阿ㄘㄟˊ
It is Amis／Pangcah (阿美族語), the language of one of the Taiwanese aborigines (台灣原住民).

阿ㄘㄟˊ ( ā céi ) means "ridiculous; crazy; unreasonable; nonsense; goofy; outrageous; nuts".

阿ㄘㄟˊ: You are nuts!

Similar phrases include 瘋了, 笨蛋, 不可理喻, 無理取鬧, 無稽之談, 胡說八道......