The rules state that you either die or fall unconscious when you have 0 hit points. The definition of “unconscious” in Appendix A specifies that you are incapacitated AND can’t move or speak AND are unaware of your surroundings.
EDIT: Maybe I shouldn’t assume you’re talking about 5e. I have no idea about 5.5e or any other edition
Yes Brave Sir Robin turned about and gallantly he chickened out. Bravely taking to his feet, he beat a very brave retreat. Bravest of the brave, Sir Robin!