There seems to be a continuous spectrum of bows from straight limbed longbows to supercurved recurves. Then to make it even more interesting, we have some recurves that aren't very recurved, and some longbows that aren't very long. We do have a clear dividing line between recurves and longbows: if the string touches the limb anywhere other than the limb tip, it is a recurve; otherwise, it's a longbow. Clear, but not very useful, because it puts some bows that perform more like recurves than straight limbed longbows into the longbow category. Probably these are the bows that are known as hybrids, which is close to what Orion said.