What's in a Name? (The Name being "Bookworm")

This was the topic of discussion in the car with my mother the other day: What defines a bookworm?

The subject came about while we were talking about a book I had been reading; I believe the author tried to paint the main character the bookish type- you know, the one that always has her nose in a book- (She'd read all Jane Austen's novels a million times through, etc.) but something about calling the girl a bookworm just didn't seem right. I couldn't figure out why.

I certainly consider myself a bookworm, as do many of you, I believe.

The dictionary defines "bookworm" as "A person unusually devoted to books or study." So my mother asked, "If that's what it means, then what separates you from her in the book world?" I struggled to grasp the right concept. Not someone who was just always reading, but someone who reads with a passion, almost...

Then something c licked within my brain as to what was the difference between the fictional girl mentioned and myself: She read so much because she was bored and had nothing else to do; I read so much because I enjoy it. I love being wrapped in another story; another world. A good book will literally give me thrills. I can't imagine that is why the formerly mentioned girl reads.

So what really defines a bookworm? Someone who merely reads often, or one who reads constantly because of the passion?