As I understand it. JBL used to sell horns with acoustic lenses. Take the HL91 for example. It is the H91 horn with the L91 lens. Today many people refer to horns with no acoustic lens as a "horn lens". I see this printed in catalogs, on eBay, and hear it in everyday conversations. This is a misnomer, isn't it?

And then there are wave guides. I assume a wave guide is like a horn in that it affects dispersion characteristics but doesn't act as a true acoustic transformer to couple the driver with the air as a horn does.