A vapour whose molecules are in dynamic equilibrium with those of its own liquid is said to be
Answer Details
The term being described in this question is "saturated." When a vapor is in dynamic equilibrium with its own liquid, it means that there is a balance between the number of molecules evaporating from the liquid and the number of molecules condensing back into the liquid. This balance happens when the vapor pressure of the liquid reaches a certain level, known as the "saturation vapor pressure." At this point, the vapor is said to be "saturated."
So, to summarize: a vapor in dynamic equilibrium with its own liquid is saturated because the number of molecules evaporating from the liquid is balanced by the number of molecules condensing back into the liquid, resulting in a certain vapor pressure known as the saturation vapor pressure.