Anime where generic protagonist with no personality is sent magically to an alternate universe and stuff, usually by being hit by a truck, just to be greeted by an army of women crazy for him for the sole reason od fulfilling weeb fantasies.

The act of being run over by a truck and being reborn in another world. A common action that happens in Anime.

Meaning: "Another world"
usually referring to Japanese stories (anime, manga, light novels or web novels) which involve the main character being transported into another world via either reincarnation, summoning, or a god transmigrating them.
the setting is usually but not always, medieval fantasy with swords and magic.

The act of sending someone to another world using particular ways, often by running them over and/or stabbing them.
Sometimes the victims of this act just get sent to the world without dying and are often seen in anime.

A Japanese genre used in anime/manga/light novel/web novel.
It is about how main characters find themselves in a different world or a different timeline.

A religion in which you don't believe in God but in reincarnation. If you die in your world instead of going to heaven or hell you will be reincarnated as the protagonist inside a Isekai World.

As an experienced otome isekai enjoyer of several years, I will give a short blurb of this genre.
Otome Isekai is a sub-genre of Isekai where the main character(s) are in some way transported to another world that resembles an otome game.

Isekai means "other world" in Japanese. Isekai stories are those where the protagonist goes to another world. Things like Escaflowne, Sword Art Online, even No-Game No-Life are all forms of Isekai.
Otome means "maiden" and "otome games" are a type of dating-sim visual novel game for girls and women. The goal is to make choices to navigate various story routes to win the hearts of different capture targets.

It is essentially the girly version of the modern shounen isekai that goes in the direction of female wish fulfillment. Instead of stuck in an action game, she's stuck in a romance novel or romance game. It is almost always "died and reborn there" rather than the sort of "stuck" we see in Sword Art Online or the "teleported" we saw in the 90s.
In general, otome isekais contain almost all of the following tropes:
1. The Main Character (MC) has foreknowledge of the events to come.
2. Our Main Character is usually a villainess.
3. Our Main Character almost always wants to avoid the "bad ending."
4. The setting is Lords and Ladies.
5. The Story is about Relationships.
6. It is written for The Female Gaze.

When you have the wish to die and reborn at a new world with the memories of your past life

A humorous and ambitious anime crossover in which 4 Isekai anime shows get transported to a school by a red button, all clustered together in one classroom.