The most basic translation is SLUT, not necessarily a paid whore or prostitute. It is normally derisive and used to label a "loose" woman, to put it nicely. In some parts of Greece, however, it is now used as an infomal term of address not meant as an insult. Think of the term "player" in the US, except as it applies to a woman. Most, however, would take the word a severe insult equivalent to "malakas" for a man.
The word originated in Greece, but it is now commonly used in Italy, Turkey, and generally the Eastern Mediterranean.
That putana from Athens was rubbing all over him as if we weren't even married!
What's up putana?
*What* did you just call me?