Nerd

A nerd is a person seen as over-intellectual, obsessive, introverted, or lacking social skills. Such a person may spend inordinate amounts of time on unpopular, little-known, or non-mainstream activities, which are generally either highly technical, abstract, or relating to niche topics such as science fiction or fantasy, to the exclusion of more mainstream activities.

https://en.wikipedia.org/wiki/Nerd