  We introduce a notion of approximate viscosity solution for a class of
nonlinear path-dependent PDEs (PPDEs), including the Hamilton-Jacobi-Bellman
type equations. Existence, comparaison and stability results are established
under fairly general conditions. It is also consistent with smooth solutions
when the dimension is less or equal to two, or the non-linearity is concave in
the second order space derivative. We finally investigate the regularity (in
the sense of Dupire) of the solution to the PPDE.
