VAC'UUM, n. [L.] Space empty or devoid of all matter or body. Whether there is such a thing as an absolute vacuum in nature, is a question which has been much controverted. The Peripatetics assert that nature abhors a vacuum.

Torricellian vacuum, the vacuum produced by filling a tube with mercury, and allowing it to descend till it is counterbalanced by the weight of the atmosphere, as in the barometer invented by Torricelli.