Plein Mind (or Plein Esprit) :
An alternative take on "Plein Air Painting" which means to paint in the open air. Plein Mind means to paint with an open mind. Plein Mind can also relate to the process of free association artistry. This occurs when the artist attempts to remove their thought process from the act of creation leaving them with an open or empty mind.
A combination of Unquenchable and Uncontainable. (Initial Usage Reference Link)