easy mark 冤大头（非正式）

英文释义
(INFORMAL) A foolish person who is overly generous, and who happily gives money to anyone.

例句
When we were children, all my cousins thought our grandfather was an easy mark because he gave them a little money for candy whenever they asked him.

在我们小时候，我的堂兄弟都觉得我们的爷爷是个冤大头，因为只要他们要求，他都会拿出一点钱来给他们买糖果。