Vacuum 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.

Vacuum 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.

Example:
We have a Vacuum that really stinks badly when turned on- any suggestions on possible remedies?

Taxonomy
vacuum, pressure, torr, gases, gauges, high vacuum, kPa, pump, particles, chamber, atmospheric pressure, inHg, perfect vacuum, measurement, MFP, existence, measure, nPa.

Defination from the web:
vacuum with a gaseous pressure of absolute zero is a philosophical concept that is never observed in practice. ... The Latin term in vacuo is also used to describe an object as being in what would otherwise be a vacuum. ...