Interested in Language
What are you short of?= What do you need?= What are you lacking to?
Do they have the similar meaning? If not, Please point me out the difference then
What are you short of?= What do you need?
It can have this meaning; if you were going to the shops and wanted to know if I need anything, either of these questions would work. However, they are not synonymous; you can need something without being short of it (I need a holiday).
What are you lacking?
This is not a normal question to me; this could be sarcastic, suggesting that the person is lacking in a quality or characteristic. Otherwise, I would not use it colloquially; it's more of a formal verb to me and I would also tend to use the simple form not the progressive.