Is a stance considered an enchantment?

and if not, is there any way to remove or take someone out of a stance? Thanks.

No, stances aren't enchantments. The only way for someone else to end them is for them to use Wild Blow but that will only end their stance if Wild Blow is blocked so most stances - the ones that matter anyway, those being the ones that end in "enzy" - can't be cancelled.