Wiktionary
n. (context Internet English) A person who claims or believes that their soul is non-human.
Wikipedia
Otherkin are a subculture people who socially identify as partially or entirely non-human. Some of them surmise that they are, either spiritually or genetically, not human, however that has yet to be substantiated. This is explained by some members of the otherkin community as possible through reincarnation, having a non-human soul, ancestry, or symbolic metaphor. Some scholars categorize this identity claim as " religious", because it is largely based on supernatural beliefs. Adherents more typically deny the religiosity of otherkinism, referring to it instead as simply a congenital condition, or a metaphysical state of being.