A chamber ballet is a chamber music performance or work that features one or more ballet dancers. Examples are a chamber music composition with the addition of dancers, or a full-scale ballet performed using a smaller ensemble.
Example of chamber ballet performance in Copenhagen: http://tokuhain.arukikata.co.jp/copenhagen/2011/10/post_92.html
Den Collinske Gaard in Copenhagen was a venue pioneering chamber ballet performance in 2010-2011: http://www.dencollinskegaard.dk/