Actually, it means "an abrupt change, sudden increase, or dramatic advance", so I think I pretty well said what I wanted to say.
In any case, now we're off to the soapbox derby. Just speaking generally, you're still falling into the teleological trap of think of evolution in terms of goals and end-products - either you have a working racer, or you have a pile of junk. Either you have a working clock, or you have a bunch of gears and springs. Either you have a fully-formed human, or you have nothing. Either you have a fully-formed bird, or you have nothing.
And it just doesn't work that way. There is no "goal" such that you can declare the intermediate steps unfit and therefore unable to have existed. Over time, a group of smallish dinosaurs accumulate changes and improvements such that they gradually become birds. Over time, a group of smallish primates accumulate changes and become early humans. Nowhere in there is there the sense that we either have fully formed book-reading humans, or we have nothing - which is exactly what I am expected to draw from the soapbox racer analogy. It's an evolutionary process, not a quantum leap from a pile of junk to the finished product. Every creature is transitional. Every creature is a "final" product. Organisms exist of themselves, according to what they are right now, not according to some standard of what they might be someday.
It's just not a very good analogy. You want to judge an organism's fitness against what it could become in the future. But it's precisely because there is no "goal" that you can't do that. All of the organisms on the planet today are still subject to selection pressures - evolution is continuing, even as we speak. All of the plants and animals around you are transitional forms that in millions of years, whose descendants very likely to bear little or no resemblance to what they are today. Now, if your analogy held true, you ought to be able to tell me what they will become, and we could then thereby judge which of the organisms that we see around us can't possibly exist ;)