"Rape culture" is the concept that some people claim to exist in modern society (usually they are talking about western cultures only) where, they say, rape is not taken seriously enough, if not even excused in many cases, victims are often blamed or too heavily scrutinized, perpetrators may sometimes be protected eg. because of their status, rape apology in general, and so on.
Some of this is true to some degree. However, it's only talking about rapes where a woman is the victim and a man is the perpetrator. There is another form of "rape culture" that's astronomically more prevalent, and which most people ignore completely (which, in itself, is part of the rape culture, of course.)
Sure, it's significantly rarer, but it does happen: Sexual harassment where the perpetrator is a woman and the victim is male.
Yes, a man can be the target of sexual harassment by a woman. The man can find the woman unattractive, unpleasant, or otherwise have zero interest in her, and not appreciate her advances at all. Not all women are meek and shy, and can be very forthcoming and intrusive, and the harassment can range all the way from words to violating personal space to improper touching and grabbing. A man can perfectly well be uncomfortable, annoyed and even feel molested by this, especially if they find the woman unpleasant and repulsive. Not all men have the strength of will nor personality to defend themselves in these situations.
This kind of sexual harassment is almost universally ignored, belittled and laughed off. People's attitude is generally dismissive and even mocking. This is basically never taken seriously by friends, peers, co-workers, employers, or even by authorities (and even if it's formally taken seriously, it's often considered of much lesser importance and urgency than if the genders had been reversed.) In fact, many people outright deny this ever happening, or having any kind of significance or relevance. If it does happen, the victim is laughed at, dismissed, belittled and called names. The perpetrator is never blamed of anything. Even people who do acknowledge that it can happen, especially the relatively rare feminist who does so, nevertheless often dismiss it as "less important" than the male-on-female harassment cases, and spend little to no effort in raising awareness of this problem.
This shaming culture is the reason why by far the vast majority of cases get unreported. Victims keep silent because they fear being ridiculed and laughed at.
If this is not the very definition of rape culture, I don't know what is.
It even goes beyond that, to a whole new level: People who bring this problem up are themselves often belittled, dismissed, called names and often accused of all kinds of things. (The mentality seems to be, for some reason, that if you bring up the problem of female-on-male sexual harassment, and especially if you are not a vocal feminist, then you somehow automatically think that the other way around is ok, ie. you are a misogynist rape apologist. I don't even understand how this logic works...)
There's another form of this kind of rape culture: Men being raped in prisons is nearly universally accepted. In fact, many people think of it as "proper punishment", especially for rapists, rather than acknowledging what it really would be as a form of punishment: A violation of human rights, which is usually (ie. in the vast majority of constitutional countries) egregiously unconstitutional.