What is the meaning of Nillionaire?

Nillionaire is not considered a dictionary word. It is a slang word made by combining the two words Millionaire and Nil. The meaning of Nillionaire means a person who has no money or wealth of his own, and is spending from someone else money. If you don't have a penny in you bank account but if you have a credit card issued to you by your bank, then you are considered a Nillionaire. Or in other context, if you don't go for a job or any source of income and you still have money to spend from the pocket money your parents are giving to you, it can also be considered as being a Nillionaire.