It is “ghostly”…
The word 鬼 gwai2 means ghost, in Cantonese, you can even use it as an adverb to emphasize your adjective.
Let’s look at this example, to say something is expensive:
|Be – Is||Adjective – Expensive|
It is “ghostly” expensive
To put an emphasis on the adjective, simply insert the word 鬼 gwai2 before the adjective. It is equivalent to these words in English:
|Be||Adverb – Emphasis||Adjective – Expensive|
“It’s freaken awesome”
|Be||Emphasis||Adjective – Expensive|
Is it polite to say?
It is commonly used and it is not impolite to say it. But in a more formal situation, you probably want to avoid saying it, for example: in front of your boss, chatting with your mother-in-law, or anyone else you take very seriously.