When a girl is sexually active she is a slut and when a guy dose it he is a stud. It is an aspect of sexism that still is all over the place. Chaste girls are pure and good, sluts are evil. It is changing but very slowly.
Ha, this shows my age: I don't know what waifu'd means
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waifu is a Japanese word incorrectly used by westerners.
A "Waifu" is a term for the focus of someone obsessed with Anime. You know like those people that have life size anime pillows that they sleep with.. that kind of thing. So the word waifu is u sally used to describe sexy or romantic anime characters that people unhealthily obsess over.
The funny thing is that "waifu" describes a male character people are in love with, not female. That is the joke which people in Japan find hilarious. All the people that talk about waifus are usually talking about women but are actually saying a word that describes a male anime charicter.
Still language is fluid and it is such a popular misconception that the meaning of the word has changed over the years to be uni-sex so to describe unhealthy sexual fandom to male or female characters. In the same way 99% of people use the word trope incorrectly, so much so that when you incorrectly use the word trope, people know what you mean anyway.
Still I always find it kinda funny all these posts you see on youtube talking about "waifu" this and that..