In art, the space around an objects is called negative space. This is the empty space, that which the subject does not fill.
In meditation, the space or consciousness around a thought is the thoughtless space, the empty space.
It is the space in between the thoughts. Not thought.
In meditation, we focus on and become aware of this “negative” space–the space around and between the thoughts, this empty space of stillness.
It is truly the most positive of things, this no-thing we meet in meditation!
The Every Day Yogi 