As a trekkie, I've seen plenty of debate about the terms. From what I've seen, 'originally' a trekkie was someone who kinda just watchedand went along with it, and a trekker was a hardcore fan. Either way, I've never run into the term 'trekker' outside of Star Trek circles that referred to Star Trek fans. Trekker, like Pegasister, is less known as a fandom term outside their respective fandom.