Source : Webster's Revised Unabridged Dictionary (1913)

Vacuum \Vac"u*um\, n.; pl. E. {Vacuums}, L. {Vacua}. [L., fr.
   vacuus empty. See {Vacuous}.]
   1. (Physics) 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.