An affliction commonly occurring in nerds that causes them to join nearby conversations uninvited. This normally occurs when the conversation is about a topic the nerd has some knowledge of.
The effects of nerdrettes can be suppressed with force of will, but many nerds lack the social grace to do so.
Man: Those people attending the game convention across the street seem to be all dressed up.
Woman: Yeah, it must be some sort of shooter game thing - see how they all have plastic guns?
Nerd: They're cosplaying as characters from the game Valkyria Chronicles. It's a turn-based military tactics game for PS3.
Man: We weren't talking to you.
Nerd: Sorry, my nerdrettes got the better of me... Do you want some Pocky?