Splicers are...[Eleanor didn't like thinking of herself that way, but after everything that had been done to her, it was...accurate enough.]

People who have had their genetic code 'spliced' with enhancements or powers. Usually with a syringe. As far as I can tell, they were just limited to Rapture...

...You know someone else who can create fire with their hand?

[Maybe there WAS a splicer here. Given how many of them were insane though...]