Stealthing is a term given to the act of removing a condom in the middle of sex, without asking your partner's permission.
A recent report from the US suggests that cases are on the rise, and that it is a hugely under-reported issue.
Twenty-two-year-old Louise (not her real name) has been telling Newsbeat it happened to her.
I thought 'that's me'
Louise says she fell victim to stealthing some time ago, but only realised after reading Newsbeat's article last month that it could have been rape.
"I saw [the article] posted. The more I read I thought, 'Oh my God, that's actually me. That's what happened to me.'
"I didn't even know it was something that happened this commonly, to be given a name."
'Friends with benefits'
Louise recalls finishing sex with a partner, and then noticing that the condom had been removed.
"It was completely casual - a 'friends with benefits' kind of thing.
"I hate that term but that is kind of how it was.
"After it had happened, we just lay there and [the condom] was on the floor.
"I said, 'I didn't see you take it off.'
"He was like, 'I did it halfway through.'
"I said, 'What? Was it an accident?'
"He said, 'No, I just thought I'd do it.'"
'Such a violation'
"For starters, it's selfish. It was such a violation. How and why would you do something like that?
"Not even to tell me, or warn me.
"He was really casual about it - saying he didn't know it would be such an issue.
"He said he thought it would be a benefit for both of us, but it was putting us both at risk.
"I just got out of there. I got my things and went.
"I phoned my friend, and asked her to come with me to a pharmacy to sort things out.
Think about the consequences
"The minute stealthing happens, he has done something then that is 'I've done this, and you can suffer the consequences.'
"One minute. That's all it takes. A change of positions and it could be gone. You wouldn't even notice.
"Think about the consequences.
"You've put your sexual health at risk, her sexual health at risk, there's the risk of pregnancy - for that however long of heightened pleasure, I suppose."
The law on stealthing
Sandra Paul is a partner in the law firm Kingsley Napley and specialises in sexual crime.
She says the law is clear - that stealthing could definitely be classed as rape.
"You're doing something that's quite deliberate, which you don't have permission for," she says.
"If that is penetrative sex, then that is the definition of rape."
No-one has ever brought a stealthing case to court, but she says there is legal precedent.
She says: "There's a case where a man failed to withdraw.
"[He and his partner] had an agreement that their method of contraception was that he would withdraw.
"On one occasion he decided that he just wasn't going to do that.
This scenario is legally similar to stealthing in that the sex act was changed midway through, so that it was no longer what had been consented to.
Ms Paul says: "The court in that case said that factual scenario was capable of being rape, and so this was something that should go in front of a jury."
The NPCC - the body that represents police chiefs - agrees.
They've told Newsbeat in a statement: "Sex without informed and freely given consent is rape.
"So-called 'stealthing' fits that definition."
They add that anyone who thinks they have been a victim should contact police.
Related: 'Stealthing' - what you need to know