Re: What does being an Uke mean to you?
It's depend. I agree with a lot of what Mary says.
When uke, if I'm with someone who's got a clue about what the movement/principle is, I like to go with the flow and learn what that person's version of what we're doing is, in case I can learn yet another variation on a theme.
When with someone new or significantly less experienced, I also go with the flow until I find a point at which I can help them be more effective (if, indeed, I can identify such a point) and depending on the situation, I'll mention "try this", or I'll stop them at the weak point in their movement and help them past it, or I'll ask the sensei/shihan over to help identify what's holding the person up, or.. or..
One of my sensei in the past said that you learn more from beginners than from experienced people. it took a while but I think I understand where he was coming from. You also learn a lot from teaching/coaching.
The folks in the "intrinsic learning" circle of research into how people learn say that teaching people by providing lots of instruction isn't that great, and that teaching by guiding the discovery through repetition and approximation (closer and closer with repeated attempts) of the ideal, people learn more slowly but better. As well, "errorless" learning, where the task starts simple and slow, getting more complex and fast as repetitions progress is also a better, more robust way to learn.
So... as uke, I like to see if I can guide the nage into really good movements (if they're less experienced), and to see if I can guide myself into better ukemi with either type of partner...