vacuum

n. void, emptiness, vacuity; space that is empty of matter; electrical device which cleans surfaces by creating air suction

v. clean with a vacuum cleaner, operate a device for cleaning carpets and floors by air suction

adj. of or pertaining to a vaccum; using a vacuum; producing vacuum

A vacuum is a volume of space that is essentially empty of matter, such that its gaseous pressure is much less than standard atmospheric pressure. The Latin term in vacuo is used to describe an object as being in what would otherwise be a vacuum. The root of the word vacuum is the Latin adjective vacuus which means "empty," but space can never be perfectly empty. A perfect vacuum with a gaseous pressure of absolute zero is a philosophical concept that is never observed in practice, not least because quantum theory predicts that no volume of space can be perfectly empty in this way. Physicists often use the term "vacuum" slightly differently. They discuss ideal test results that would occur in a perfect vacuum, which they simply call "vacuum" or "free space" in this context, and use the term partial vacuum to refer to the imperfect vacua realized in practice.
See more at Wikipedia.org...

n. vacuum, void, emptiness

n. vacuum, void

(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.
  

(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.