:] I'm not "making up" the definitions, and I find that characterization needlessly dismissive. I'm describing how the different terms are widely used in the industry and in society. "UFO" carries undeniable connotations of mystery and eerieness. The "U" stands for "unidentified," after all, and the UFO mythology that's evolved in society since 1947 is basically the Space-Age version of ancient beliefs and fears about fairie folk and demons. This isn't just my opinion; there are whole scholarly studies about the UFO cult and culture.
As for your first paragraph, I can imagine possible meanings for "entity" beyond what you suggest, but since you sadly seem more determined to narrow your perspective than attempt to broaden it, I don't see why I should waste my time suggesting any.