Poor mouth refers to someone who continually complains about a lack of money, often as an excuse for not contributing to charities, paying bills, etc.

Poor mouth指那些老抱怨自己没钱、并以此为借口逃避付账单或者为慈善事业捐款的人，我们可以称之为“哭穷鬼”。

For example: 

She is a real poor mouth. She has a brand new car in her driveway, but always delays paying her rent.

她是个不折不扣的哭穷鬼。她家门口停着崭新的车，但总是拖着不付房租。