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。

When used as a verb, the term poor-mouth means to lament or argue that one is too poor; plead poverty, or to declare (one's ability, power, position, etc.) to be inadequate or disappointing, sometimes as an intentional understatement.

这个说法用作动词时是poor-mouth，可以指“哭穷”这个本意，也可以指故意自我贬低，说自己的能力、地位、权力等不够高等。

For example:

We know you're just poor-mouthing your skill at playing bridge—you're a good player.(dictionary.com)

我们知道你在故意说自己的牌技差，你其实是桥牌好手。

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