I kind of like the term "thruster" myself. But yeah, I use "motor" and "engine" interchangeably when I am talking about rockets. As far as I am concerned, the two terms are synonymous. Perhaps that's wrong from an engineering perspective, but I'm not an engineer anyway.
If I was writing a paper for a professional engineering publication, I would be more careful and precise in my terminology, but in everyday conversations (and posts on forums), it really doesn't matter which term I use. Everyone seems to know what I mean.