A woman who is considered to be dangerously seductive.
A "Femme Fatale" is in most cases a criminal woman who uses her beauty and seductive skills in order to achive her goals, wich can range widely from assassinating an unsuspecting victim or simply pickpocketing a common civilian. Most of their victims happen to be hetrosexuall (straight) men for obvious reasons. It is very common in fiction that male heroes tends to go very easy on these kinds of villians due to underestimation of the beautifull opponent or simply a lack of self-control (or in a lack of better words: got the hots for the bad girl). Most female heroes in fiction will do the direct opposite against the Femme Fatales and fight even harder than they normaly do against other opponents due to envy or unacceptance of other heroes lack of competence, wich usually leads to a catfight filled with fanservice for innocent bystanders to enjoy.
Though most Femme Fatales are simply common thieves who uses a decieving mixture of beauty, intellect, agility and swiftness to silently steal a wallet, there are those who takes more risky jobs were their skills can come in handy. Some of these jobs can include espionage, infiltration, kidnapping, blackmailing or even assassination. Many females ninjas (kunoichi) follows the ways of Femme Fatale, wich can explain why they sometimes uses similar disgueses for different kinds of missions. These disgueses can range from dancers, singers, entertainers, maids or even prostitutes.