My understanding of it is a system of ownership and direction of enterprizes, where the state participates as a capitalist and as managenent, either wholely or in concert with private ownership.
You know, like Lennin meant
edit to add: Lennin was certainly against any private participation in capitalism, but the soviet party did loosen that with parastroika, and the Chinese Communist party started with, I believe, Deng Xiaping Thought, tho I would have to double chetk that it didn't start earlier