A noticably empty space, such as a defect like a bubble in a (generally solid) material.
To cause to be invalid (i.e. to void a check).
Often used as the title of the fifth Scroll in Miyamoto Musashi's The Book of Five Rings (better translations are "Nothingness" or "Emptiness"). Musashi defines this Void as "the realm where nothing exists, or cannot be known," and notes that "wrongly viewed among people of the world, not understanding anything is itself considered void. This is not real void; it is all a delusion."
