  We consider the situation where the luminosity from a transient event is
reprocessed by an optically thick wind. Potential applications are the tidal
disruption of stars by black holes, engine-powered supernovae, and unique fast
transients found by current and future wide-field surveys. We derive relations
between the injected and observed luminosity for steady and time dependent
winds, and discuss how the temperature is set for scattering-dominated
radiative transport. We apply this framework to specific examples of tidal
disruption events and the formation of a black hole by a massive star, as well
as discuss other applications such as deriving observables from detailed
hydrodynamic simulations. We conclude by exploring what is inferred about the
mass loss rate and underlying engine powering AT2018cow if it is explained as a
wind-reprocessed transient, demonstrating that its optical emission is
consistent with reprocessing of the observed soft X-rays.
