Slut - what actually makes out a "slut"?
Is it the many partners he/she had intercourse with?
Is it the many people which he/she let touch his/her body, kissed?
Is it the style according to which he/she does all that?
Or just if he/she does it thoughtlessly - not making much selection between the people he/she does it with? Not taking care of protection from unwanted mother-/fatherhood/transmittable diseases?
What exactly is it that makes a person "slutty" compared to other people?
Socially, there are two standards for measuring: One originates from the interpretation of the term as "sloppy". Doing things sloppy and unfinished, or finished badly and not thoroughly enough, not taking enough care about one's looks and literally neglecting one's outside appearance.
The other definition originates from moral decay - acting hedonistically, selfishly, recklessly and ruthlessly. Primarily measured by one's mating behavior, including sexual intercourse.
So to say, by those definitions, a "slut" is a person which dresses and behaves trashy, whose self-respect is lowered, which acts too carelessly, doesn't invest too much energy into one thing, lives hastily and tends to flee from things after they don't give the right dosage of satisfaction anymore - "sluts" also tend to pickup the most in life regardless of if they'd be morally permitted to or not, rather than giving anything back in return.
In other words, "parasite", on the whole, would rather be a better synonym than just "someone who is promiscuous".
Tolerance and acceptance of promiscuity are cultural issues; Christian religion sanctioned it over centuries and linked it with shame, installing the one-partner-at-a-time exclusiveness that is still common in most of the world's areas.
This hasn't always been this way - this is a matter, a standard, which can be shifted and made to change again, just like it could be shifted to the standard that still is prevalent today. It is not unchangeable.
In earlier centuries more, but still of some relevance in the modern times, it had its practical purpose in order to create more safety for an individual's health and in order to prevent too much intra-familial incest - as the only safe contraception and block to diseases which spread by sexual intercourse for the general populace was simply not doing it.
Partner-exclusiveness through marriage and loyalty to its basic principle meant, two at the same time, that diseases couldn't spread that wildly (that is: if one was sick, he could only pass it on to one other person) and that children in a small community couldn't be that many half-siblings from both mother- and father-family-bloodline among themselves which they never got to know about until they chose a partner inside the community and had one unhealthy child after another with each other.
Today, technically, the need for this measure doesn't exist anymore. It's a question of money, of having access to as much contraception means as one needs for his/her lifestyle, and of human laziness to take care of it or not. Maybe of taboo - in certain circles - and of general sex education in certain proportions still too.
So... that entirely making out a "slut's" behavior is like an artificial standard now. And this needn't be exclusively limited to females.
There are ways meanwhile to practice promiscuity safely.
So... what is there else?
Maybe if he/she practices it without taking care of his/her own and their partner's physical integrity? If the person behaves irresponsibly against better knowledge and against the means available to him/her?
If a woman has three children from three different men differing in not so many years of age - if a man fathered 3 children with 3 different women during the same few years, for example?
If a couple keeps begetting a baby every year to keep their social benefits?
...Easier it is to answer if sticking to the definition of "doing one's job sloppily". Or with the circumstance of neglecting oneself's appearance fully voluntarily.
'Cause a job done badly doesn't always have anything to do with morals, which can be shaped individually and don't have to be objective. Disregard of personal hygiene or overacting in it in a perverted twisted way can follow a subjective pattern that doesn't have to be factually correct, but to a certain minimal extent, it also has an objective core which moving beyond may end up turning harmful for oneself as well as other people.
In other words: It's easier to find a common base and that doesn't always need to have to do with an individual's personal perspective.
Some negative personality traits, or behavior, just tends to cause always trouble, no matter where the individual pops up which shows them. And there even is more than subjective way to feel to it to perceive it like this.
So... what remains at the end of this?
There's more than meets the eye in one's current filter bubble if thinking things through more widely...