Supposably
Well, it's not a real word. So maybe it doesn't count. I'm all for made up words, but when people use this word, it usually sounds like they've intended it to be a proper word.

Could care less
Yes, it's a phrase, not a word. So I'm a cheater at this prompt.
However, it's an inaccurate phrase; it makes no sense. I am forced to bite my tongue when people say "Well I could care less" because the appropriate response is "Well then GO FOR IT"... but that would make me a total bitch, and I strive not to be.
If you could NOT care less, however, I cannot challenge that, and understand your point of view.