A mixture of a FreeMarket and regulatory controls, such as exists in the UnitedStates at present.
I understand a MixedEconomy to be a FreeMarket where the State not only regulates but owns substantial pieces of the national economy. As in, nationalized industries. Different from a CommandEconomy? in that prices are not regulated by the State and there is still freedom to contract.
If regulatory controls were enough to make a FreeMarket into a MixedEconomy, then FreeMarket can't be a useful term (to describe actually existing national economies) because there would be no such thing. Every nation regulates commerce.