Every time I think I have my head around what these terms mean I seem to run
across someone with a completely different definition.

My understanding was that the singleton class is what you obtain when you
call self.class in instance scope, and that metaclass and eigenclass
are interchangeable terms for what you obtain if you call class << self;
self; end in instance scope.

Is this correct? Do you have a different definition?

-- 
Tony Arcieri
Medioh! A Kudelski Brand