a person, especially a man, who is not attractive and is awkward or socially embarrassing

He was a real nerd in high school - I can't believe he's so handsome now. 他上高中的时候呆头呆脑——我简直无法相信他现在这么帅。

a person who is extremely interested in one subject, especially computers, and knows a lot of facts about it

I'm a real grammar nerd. 我真的是一个语法迷。