Due to being asked to put this up here, I will. After all, it's only polite!
A swot is someone who studies a lot and is generally very intelligent. Generally viewed with some contempt due to not having a life beyond school.
Basically, a nerd by any other name, although I don't think swots have the same connotations of being science-fiction or movie freaks...they just study a lot. Also I think it's slightly less perjorative.