1. (n.) A space entirely devoid of matter\ (called also, by way of distinction, absolute vacuum); hence, in a more general sense, a space, as the interior of a closed vessel, which has been exhausted to a high or the highest degree by an air pump or other artificial means; as, water boils at a reduced temperature in a vacuum.

2. (n.) The condition of rarefaction, or reduction of pressure below that of the atmosphere, in a vessel, as the condenser of a steam engine, which is nearly exhausted of air or steam, etc.; as, a vacuum of 26 inches of mercury, or 13 pounds per square inch.

absence absence of mind blank blankness broom brush brush off clean slate deprivation emptiness empty space empty-headedness hollowness inanity jejunity mental void negation negativeness negativity nihility nonbeing nonentity nonexistence nonoccurrence nonreality nonsubsistence not-being nothing nothingness nullity sweep sweep out sweep up tabula rasa unactuality unreality vacancy vacuity vacuousness vacuum-clean vapidity void whisk