Urban Dictionary: fc

fc. flirt capacity. its what girls or rather gay guys say when talking about how much they flirt with guys. it is possible to have an fc of 0-100, 0 being incredibly unsocial when it comes to the opposite (or same, depending on your sexuality) sex, and 100 being a whore. the average teenage girl with a lot of friends probably has a 30-75 fc. flirt capacity loser whore popular.

https://www.urbandictionary.com/define.php?term=fc