09/02/2015 12:39 GMT | Updated 11/04/2015 06:59 BST

As Girls and Women, Anyone at Any Moment Can Decide That We're a 'Slut'

Since I started The UnSlut Project by posting my middle school diary online back in 2013, I've heard from a lot of teenage girls from all over the world. Some of them want to share their stories of overcoming sexual bullying. Some of them are in crisis and want to know where to go for help. And some of them want to know how to avoid being labeled a "slut," like I was at their age. They ask me, "How should I dress?" "Should I date this boy?" "What can I do to make sure this doesn't happen to me?"

And I have to let them in on an unfortunate, tragic truth. There is no way to avoid being called a slut.

Nearly every woman I have spoken to about The UnSlut Project has confided in me that at one point in her life, she, too, was labeled a "slut." Maybe it was by the man whose advances she rejected at the bar. Maybe it was by the woman who accused her of stealing a boyfriend. Maybe it was by a coworker who was suspicious of her new promotion.

Women with many sexual partners are "slut" shamed, but so are virgins. Women who live alone are "slut" shamed, but so are married, full-time mothers. Girls who wear clothing that clings to their bodies are "slut" shamed, but so are girls who dress conservatively.

It's not about you. It's about the person who is "slut" shaming you and their assumption that "slut" shaming even makes sense.

That's why when I witness someone using the word "slut," I ask them to define it. In fact, The UnSlut Project shirts say DEFINE "SLUT" across the front. Wearing one is always a conversation starter, with friends and strangers alike. (In fact, you should get one! All you have to do is contribute to our crowd-funding campaign for "Slut: A Documentary Film."

The point is, "slut" means whatever the person using it as an insult wants it to mean. When I ask people to define it, they often say something like, "A slut is a woman who is promiscuous." I reply, "What's promiscuous?" They answer, "Well, it means she sleeps with too many men." I follow up with, "How many men is too many?" At this point, they usually start chuckling, because they realize how ridiculous the whole thing is. They might come up with a number that they believe is "too many," but usually they admit that the insult makes no sense. Because there is no one definition of "slut."

And that's why it's so dangerous. As girls and women, we know that at any moment, anyone could decide that we are a slut. We have no say in the matter. And once a rumor like that gets started, it sticks. We can't control it, and that's terrifying.

So when a girl asks me what she can do, I tell her there's no way to avoid being "slut" shamed, because she doesn't get to decide what the definition of a "slut" is when that label is applied to her. But she does get to decide how it affects her.

Even though she can't define "slut," she can define herself. Especially as adolescents, we often depend on other people to decide who we are and what's important about us. Instead of giving others that power, she can focus on what she likes doing, what she's good at, and the healthy relationships in her life. She can be an athlete. She can be funny. She can be intellectually curious. She can come up with a new definition for herself, one that doesn't depend on anyone else's arbitrary definition of the word "slut."

You can contribute to the crowd-funder for Slut: A Documentary Film here