How to define emptiness? Is it simply absence of something? Or absence of something's previous presence? Or either?
'Define' may not be the right word to question, how about 'perceive'? Emptiness remains the same.
When something is not perceived, does it imply absence of something? Emptiness is created, out of transient void? If so emptiness is what exist at the beginning. Gets filled in the same way water fill the void it flows through.
Emptiness is the big bang of mind? Filled as stuff we perceive? Emptiness is always there within us. Absence of something only exposes what exists before.