It's hasn't become "meaningless". Its quite simple to understand.
If you don't support the basic tenets of the GOP party platform, then you're a RINO. Further, if you don't support the basic tenets of the conservative agenda, then your a CINO. Pretty straightforward.
>>>In my mind, RINO now means someone who votes for a candidate who can actually win.
Wrong. That means you're a wishy-washy centrist, aka.RINO. Without conservative principles and without Republican conviction.
Boy do you make my point. You have no idea what my conservative principles are, but you call me a RINO because I don't believe exactly the same as you. RINO is a meaningless word, because you use it as a name to call anyone who doesn't toe your perfectionist line. It must be tough, because you will never find the perfect candidate, except for maybe Alan Keyes.