Terminology - Motor vs. Engine

[rbattelle]

In your opinion, what's the difference between a motor and an engine?

Some people refer to the thing under their hood as a "motor".

I've heard people refer to large electric motors as "engines".

Personally, I define them like this:
motor - a device which accepts energy input and produces work. Without external energy supply it is useless.

engine - a device which produces its own energy and converts it to mechanical work.

Any electric motor, which requires power input from an engine (ie a generator), is therefore a "motor".

Any internal combustion engine, which independently converts chemical energy to mechanical energy, is an "engine".

What do you all think? I'm certain there are other ways of looking at it. Webster seems to suggest the two terms are nearly interchangeable.

Ryan