  We propose a definition of viscosity solutions to fully nonlinear PDEs driven
by a rough path via appropriate notions of test functions and rough jets. These
objects will be defined as controlled processes with respect to the driving
rough path. We show that this notion is compatible with the seminal results of
Lions and Souganidis and with the recent results of Friz and coauthors on fully
non-linear SPDEs with rough drivers.
