A Female who in the time of 5 years has had sex with more than 15 people. Roughly a 3 to 1 relationship in terms of years to times she has had sex. Kissing doesn't matter see kissing slut or kissing whore.
Any kind of cheating or multiple partner relationship time intervals also demands the designation of a slut. Sluts usually have very loose vaginas because they let guys put lots of different things in there, the more guys the looser.
1: Sally gets fucked by so many different guys every week. She's a fucking slut.
2: My girlfriend told me she has had sex with "probably ten" guys before me. She is a slut, because she's only 18.
3: Jessica cheated on her boyfriend. She is a slut.
4: Her pussy is so loose, I had no idea I was dating a slut.
5: I put three sometimes four fingers in her when I finger her. She is loose like a slut.