Torricellian \Tor`ri*cel"li*an\, a. Of or pertaining to Torricelli, an Italian philosopher and mathematician, who, in 1643, discovered that the rise of a liquid in a tube, as in the barometer, is due to atmospheric pressure. See Barometer.

Torricellian tube, a glass tube thirty or more inches in length, open at the lower end and hermetically sealed at the upper, such as is used in the barometer.

Torricellian vacuum (Physics), a vacuum produced by filling with a fluid, as mercury, a tube hermetically closed at one end, and, after immersing the other end in a vessel of the same fluid, allowing the inclosed fluid to descend till it is counterbalanced by the pressure of the atmosphere, as in the barometer. --Hutton.

Source: Webster's Revised Unabridged Dictionary (1913)