VolVol is a Quotable that represents in Deriscope usage the commonly known "volatility" of the stochastic process associated with a given Quotable at some fixed future time (maturity).
The stochastic process is defined inside an input parameter of type Vol Spec.
If that process is multidimensional (driven by several risk factors) then the overall volatility is also multidimensional.
The type of volatility used here refers to a single component of the overall volatilty, in other words a volatility with respect to some single risk factor.
That risk factor is also specified in Vol Spec.
Finally due to the several different ways that a volatility may be mathematically defined, the Vol Spec also provides the exact type of volatility.
More details on the mathematical definition of volatility can be found in Vol Spec.