Somebody with a BDSM bent who has lighted up an interest in it at well before puberty. In other words "as long as they can remember". An innate perv; somebody who really liked to be bound to the pole during play, or to be the one to tighten the knots. Statistically rare.
This trait is somewhat correlated with atypically rigid sexual objects or rituals of desire, as well as political advocacy for "perv rights". As in "no, I can't come until you impale me" or "you might as well fuck off if you can't deal with my feces".
"Dunno, she's just so into the stuff. Maybe she's a lighter or something."
"I just don't understand the thing with the needles." "Relax, that's just a part of him. He's a lighter."
"For the longest time I thought it was just for thrills, but then he told me he's actually a lighter."