For me, a crank is an professor—there are crank independent researchers, and so on, but we need not be concerned with them—who have no followers or school to speak of. I won’t name names, but you know who they are, at least in whatever subareas you work. Linguistics has a lot of cranks, and one place you’re particularly likely to encounter them is at events hosted by the Linguistics Society of America (LSA). The first LSA talk I ever went to (back in 2007, in Anaheim) was by an infamous crank, and I was discouraged to find out that everyone in the audience except for me seemed to know this guy was a charlatan who had been spinning this line for years. This is in contrast to, say, equivalent events in Canada (CLA/ACA) or the UK (LAGB): at such institutions, cranks can be seen but generally not heard. Given the LSA’s current mission to encompass all of linguistics, I see why this is, but it seems more should be done to prevent corruption of the youth by the usual suspects.