Insult garnered from a particularly severe haircut on males where a nearsighted barber has trimmed around the ears perhaps a little too drastically and has left a visible line of pale flesh around the ear/head interface.

The percentage off increased proportionally with the size of the gap between ear and hairline with claims of 50%, 90% and even a particularly ambitious cry of "Ear clearance, FREE!" by a random year 9 who didn't note that the guy was just bald...

Richard 'Grizzly' Adams, IT teacher to the masses once turned up after half term with an amazing 2" clearance.

I had completely forgotten about this until I saw the conductor on the train from Derby to Nottingham a month or so back who had a rather tasty 2cm clearance.