I'm sure that definition would vary somewhat depending on where you find it. But by that definition, the flies I tie on jig hooks are not jigs because I don't fish them in a vertical motion. I would also guess the first tyer who used synthetic materials was scoffed at, too. I don't see that what type of hook you tie your imitation on makes it a "fly" or not.Definition I found online:
?Jigging is the practice of fishing with a jig, a type of fishing lure. A jig consists of a lead sinker with a hook molded into it and usually covered by a soft body to attract fish. Jigs are intended to create a jerky, vertical motion, as opposed to spinnerbaits which move through the water horizontally.?
Joe