That's funny because I've never heard of prophetic dancing. LOL.
Prophetic singing usually refers to a song that is given to the singer from the Lord on the spot. Pastor Jackson does that a lot, although I've never heard him call it prophetic singing. He'll start preaching/exhorting about something, and then start singing it, and then from there, lyrics and verses come to him and he just sings it... he did that one time about a year ago and sang an entire song with like 3 or 4 different verses. It was kinda amazing to watch. There's a young lady in Atlanta who is very gifted in this area. No matter what she sings, just about every time she gets up, she ends up flowing into something else that really blesses and ministers to the people and to God.
I guess another way of describing it would be "impromptu" singing, or maybe "freestyling"
which really may not convey what is actually taking place... and that's probably why they call it prophetic singing.
A lot of people are gifted like that, but most people don't label it "prophetic singing."