Perfistent adjective /pəˈfɪs.tənt/
Someone who refuses to stop during the sexual act of fisting.
Mary: How was your fisting session with that bull-dyke you pulled last night?
Nicole: Painful! I’d cum 5 times and begged for her to untie me but she just wouldn’t stop.
Mary: Perfistent slag.
Nicole: Yeah... I’m seeing her again tonight.