  In the Mott insulating phase of the transition metal oxides, the effective
orbital-orbital interaction is directional both in the orbital space and in the
real space. We discuss a classical realization of directional coupling in two
dimensions. Despite extensive degeneracy of the ground state, the model
exhibits partial orbital ordering in the form of directional ordering of
fluctuations at low temperatures stabilized by an entropy gap. Transition to
the disordered phase is shown to be in the Ising universality class through
exact mapping and multicanonical Monte Carlo simulations.
