It means "permanent voraphilia". It's a fetish in which one fantasizes about being eaten alive or eating another creature permanently.

Usually, in roleplaying, permavore means that the characters being eaten will become unusable from now on. A character who has been prey in a permavore fantasy is considered "dead" by his creator and never used again.
— Yesterday, I use my character "Tobias" in a permavore fantasy.

What a waste! ¿Can't you still use him?
— Nah, he's gone for good. It was a great character but it was worth it.
by TheHelpingJoe February 8, 2019
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