1. Don't act like a stupid person in front of others.
别在别人面前表现得像个傻瓜。

2. He felt like a stupid person for making that mistake.
他因为犯了那个错误而觉得自己像个笨蛋。

3. Only a stupid person would believe such a lie.
只有傻瓜才会相信这种谎言。

A: Why did he throw his phone away?
A：他为什么要把手机扔了？

B: I think he is being a stupid person.
B：我觉得他表现得像个傻瓜。

1) 傻瓜

2) 笨蛋

3) 蠢人

1. 傻瓜，愚蠢的人

e.g.
Stop acting like a stupid person.
别再表现得像个傻瓜了。

noun phrase

1. A person who lacks intelligence, common sense, or good judgment.

Synonym: fool, idiot, moron