I was flicking through a copy of George Saunders' The Braindead Megaphone today and ran across this quote. It might be the most insightful definition of humor I've ever heard.
Humor is what happens when we're told the truth quicker and more directly than we're used to. The comic is the truth stripped of the habitual, the cushioning, the easy consolation. An "auditorium filled with two thousand men and women eagerly awaiting a night's entertainment" could also correctly be described as "two thousand smiling future moldering corpses" or a mob of bodies that, only hours earlier, have, during the predressing phase, been standing scattered around town, in their underwear."