A science geek is an NPC that is featured in The Sims 3, who are usually seen when a house infested with bugs has a new household moved in it. They come and ask the house's owner if they can take the bugs in order to study them. Most usually have the computer whiz trait, though there are some exceptions, such as Griffin Torrent, Jane March, etc.
While most worlds in The Sims 3 come with a pair of one male and one female for each base game NPC type, science geeks are an odd exception. Some worlds, such as Sunset Valley, do have one male and one female pre-made science geeks. Others, like Bridgeport, [TS3:LN] have just one pre-made science geek.