Learner's definition of NERD
[count]informal + usually disapproving
1 : a person who behaves awkwardly around other people and usually has unstylish clothes, hair, etc. 2 : a person who is very interested in technical subjects, computers, etc.
— nerdish/ˈnɚdɪʃ/adjective,[more nerdish; most nerdish]
— nerdy/ˈnɚdi/adjective,nerdier; nerdiest[also more nerdy; most nerdy]