nerdnoun [ C ] uk ​ /nɜːd/ us ​ /nɝːd/ informal disapproving. › 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. › 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.