- In slight contrast to her maybe-sister
I don't even know what a "nerd" is anymore. I can ask people and get answers, sure, but they'll vary greatly. Some will refer to a particular group of hobbies or interests, others will refer to a set of behavior that is applicable to any hobby or interest, while still others will consider the term synonymous with "intelligent" at the exact same moment others are saying it's synonymous with "loser".
I personally tend to use the term when jokingly referring to particular hobbies or interests. Fantasy, Sci-Fi, comics, etc. Those aren't exactly things with tiny cult followings these days, however, and I feel "nerd" is best used to describe someone with a particularly obsessive interest with just about anything.
Granted, words are allowed to have multiple definitions based on usage, so I suppose all of the above and more are valid uses of the word "nerd". Kind of limits its practical uses if it can mean everything and the kitchen sink, but there you go.