Non-anime characters depicted in an anime art style. This can apply to characters from live action television shows/movies, cartoons, western comics, and video games, as well as real people.
Does not apply to characters from western comics or cartoons that already have anime-like designs. (e.g. Avatar: The Last Airbender, RWBY, Peni Parker from Spider-Man: Into The Spider-Verse)
Note: Some sites use the term "animification" to refer to art depicting humans or objects as animals. On Danbooru that concept is tagged as animalization.