It's hard to define a slave vs. a submissive when there are so many variances to the human thought. Submission is defined so different to everyone as is dominance. And because of that there are many myths because it's easy to generalize.
I was explaining to a girl I work with how I submit to my Owner in the bedroom and in our home, but not in front of our son or in public. And part of that is being clearly verbal about anything. I don't communicate often. It's easier for me to just not say anything and bottle up what I am thinking and feeling. Being forced to speak about my concerns or problems, or even my day, is a submissive thing for me to do b/c I don't like doing it. If given a choice I'd rather not tell him anything and just be quiet.
She actually thought this was odd b/c she always though that slaves/submissives were treated like children "you don't speak unless spoken too," and a Dominant doesn't want to hear your problems or complaints, it's a just "do as you're told" situation. I explained he genuinely cares about what I think and feel and wants to hear it, and he values that the communication will keep our relationship functioning. And so one major way I submit to him is to verbalize my feelings. While to other people, that isn't submissive at all, it may even be the opposite for them. To me, that's submitting to his will and needs.