He has already told us what his definition is: it's half one thing and half something else. For Ray, a fossilized mermaid would be what he calls a transitional form. That is no misrepresentation of Ray's caricature of evolution. Here is his own representation of how he thinks evolution happens:
The next obvious question when presented with this level of ignorance -- perhaps not the immediately next, as so many questions come to mind -- is: "What about Platypus?"
Note that the platypus is an "egg-laying, venomous, duck-billed, beaver-tailed, otter-footed mammal." According to Ray, doesn't this qualify as his transitional form of some duck to a beaver, thus conforming to his misunderstanding of evolution? Of course not. As with any Young Earth Creationist, any evidence to the contrary is just how God created it. (Watch the first minute:)
Kirk later says regarding transitional fossils, that "as far as [he] understands, any fossil that you find in your museum is a fully formed creature. There is not something in there that is halfway between on animal and halfway between another animal that you can observe to be so." But let's not forget what he had just said after stating that there are, according to his research and understanding, no transitional forms:
"Wait a minute, look at the platypus. There is a mammal with hair and a bill like a duck." Yeah, it's a strange one and that's exactly how God made it. And there's plenty of strange animals like that.