Nillionaire refers to a person who has very little money. The term is a portmanteau of nil and millionaire, where the word nil means zero or nothing. (Source: Merriam-Webster Online)

Nillionaire指手里没什么钱的人，也就是“穷光蛋”。这个词是nil和millionaire（百万富翁）两个词混合而成的，nil的意思就是“零”、“无”。

For example:

I am sick of being a nillionaire.

我受够了当穷光蛋的日子。