I don't know, I've always known trolls to be members of forums (or generally people on the internet) with the intention of creating problems, upsetting people, causing arguments, etc. Not people who just happen to be idiots/etc, but people whose purpose for being on a forum/website/on the internet is to intentionally, purposefully, knowingly create problems. Often by lying about who they are, or joining forums/websites they have no genuine interest in, etc.
But maybe I'm outta touch!